[Federal Register: December 10, 2002 (Volume 67, Number 237)]
[Proposed Rules]
[Page 76055-76094]
From the Federal Register Online via GPO Access [wais.access.gpo.gov]
[DOCID:fr10de02-19]
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Part VII
Department of Health and Human Services
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Food and Drug Administration
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21 CFR Part 1020
Electronic Products; Performance Standard for Diagnostic X-Ray Systems
and Their Major Components; Proposed Rule
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DEPARTMENT OF HEALTH AND HUMAN SERVICES
Food and Drug Administration
21 CFR Part 1020
[Docket No. 01N-0275]
RIN 0910-AC34
Electronic Products; Performance Standard for Diagnostic X-Ray
Systems and Their Major Components
AGENCY: Food and Drug Administration, HHS.
ACTION: Proposed rule.
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SUMMARY: The Food and Drug Administration (FDA) is proposing to amend
the performance standard for diagnostic x-ray systems and their major
components. The agency is taking this action to update the standard to
account for changes in technology and use of radiographic and
fluoroscopic systems as well as to fully utilize the currently accepted
metric system of units in the standard. For clarity and ease of
understanding, FDA is republishing the complete contents of the
affected regulations. This action is being taken under the Federal
Food, Drug, and Cosmetic Act (the act), as amended by the Safe Medical
Devices Act of 1990 (SMDA).
DATES: Submit written or electronic comments by April 9, 2003. See
section III of this document for the proposed effective date of a final
rule based on this document. Submit written comments on the information
collection requirements by January 9, 2003.
ADDRESSES: Submit written comments to the Dockets Management Branch
(HFA-305), Food and Drug Administration, 5630 Fishers Lane, rm. 1061,
Rockville, MD 20852. Submit electronic comments to http://www.fda.gov/dockets/ecomments.
Submit written comments regarding the information
collection requirements to the Office of Information and Regulatory
Affairs, Office of Management and Budget (OMB), New Executive Office
Bldg., 725 17th St., NW. rm. 10235, Washington, DC 20503, Attn: Desk
Officer for FDA.
FOR FURTHER INFORMATION CONTACT: Thomas B. Shope, Center for Devices
and Radiological Health (HFZ-140), Food and Drug Administration, 9200
Corporate Blvd., Rockville, MD 20850, 301-443-3314, ext. 132.
SUPPLEMENTARY INFORMATION:
Table of Contents
I. Background
II. Proposed Amendments to the Performance Standard for Diagnostic X-
Ray Systems and Their Major Components
A. Change in the Quantity Used to Describe X-Radiation From
Exposure to Air Kerma
B. Clarification of Applicability of Requirements to Account for
Technological Developments in Fluoroscopic X-Ray Systems Such as
Digital Imaging, Digital Recording, and New Types of Solid-State X-Ray
Imaging Devices
C. Changes and Additions to Definitions and Applicability
Statements
D. Information to be Provided to Users (Sec. 1020.30(h))
E. Increase in Minimum Half-Value Layer (Sec. 1020.30(m)(1))
F. Change in the Requirement for Fluoroscopic X-Ray Field
Limitation and Alignment (Sec. 1020.32(b))
G. Revisions and Change in the Limits to Maximum Air Kerma Rate
(Sec. 1020.32(d) and (e))
H. New Modes of Image Recording
I. Entrance Air Kerma Rate at the Fluoroscopic Image Receptor
J. Requirement for Minimum Source-Skin Distance for Small C-Arm
Fluoroscopic Systems (Sec. 1020.30(g))
K. Requirements for Display of Fluoroscopic Irradiation Time, Air
Kerma Rate, and Cumulative Air Kerma (Sec. 1020.32(h) and proposed
(k))
L. ``Last-Image Hold'' Feature on Fluoroscopic Systems (Proposed
Sec. 1020.32(j))
M. Modification of Previously Manufactured and Certified Equipment
N. Modification of Warning Label (Sec. 1020.30(j))
O. Corrections of Sec. 1020.31(f)(3) and (m)
P. Corrections to Reflect Changes in Organizational Name, Address,
and Law (Sec. 1020.30(c), (d), and (q))
Q. Removal of Reference to Special Attachments for Mammography
R. Change to the Applicability Statement for Sec. 1020.32
S. Republication of Sec. Sec. 1020.30, 1020.31, and 1020.32
III. Proposed Effective Date
IV. Environmental Impact
V. Paperwork Reduction Act of 1995
VI. Analysis of Impacts
A. Introduction
B. Objective of the Proposed Rule
C. Risk Assessment
D. Constraints on the Impact Analysis
E. Baseline Conditions
F. The Proposed Amendments
G. Benefits of the Proposed Amendments
H. Estimation of Benefits
I. Costs of Implementing the Proposed Regulations
J. Small Business Impacts
K. Reporting Requirements and Duplicate Rules
L. Conclusion of the Analysis of Impacts
VII. Federalism
VIII. Submission of Comments
IX. References
I. Background
The SMDA (Public Law 101-629) transferred the provisions of the
Radiation Control for Health and Safety Act of 1968 (RCHSA) (Public Law
90-602) from title III of the Public Health Service Act (PHS Act) (42
U.S.C. 201 et seq.) to chapter V of the act (21 U.S.C. 301 et seq.).
Under the act, FDA administers an electronic product radiation control
program to protect the public health and safety. FDA also develops and
administers radiation safety performance standards for electronic
products.
The purpose of the performance standard and these proposed
amendments is to improve the public health by reducing exposure to and
the detriment associated with unnecessary ionizing radiation from
diagnostic x-ray systems while assuring the clinical utility of the
images.
In order for mandatory performance standards to provide the
intended public health protection, the standards must be modified when
appropriate to reflect changes in technology or product usage. A number
of technological developments have been or will soon be implemented for
radiographic and fluoroscopic x-ray systems. Such developments,
however, are not addressed in the current standard, but have presented
problems in the application of the current performance standard.
FDA thus is proposing to amend the performance standard for
diagnostic x-ray systems and their major components in Sec. Sec.
1020.30, 1020.31, 1020.32, and 1020.33(h) (21 CFR 1020.30, 1020.31,
1020.32, and 1020.33(h)).
These proposed amendments will require additional features on newly
manufactured x-ray systems that physicians may use to minimize x-ray
exposures to patients. Advances in technology have made several of
these newly required features possible or feasible at minimal cost.
In the Federal Register of August 15, 1972 (37 FR 16461), FDA
issued a final rule for the performance standard, which became
effective on August 1, 1974. Since then, FDA has made several
[[Page 76057]]
amendments to the performance standard to incorporate new technology,
to clarify misinterpreted provisions, or to incorporate additional
requirements necessary to provide for adequate radiation safety of
diagnostic x-ray systems. (See, e.g., amendments published on October
7, 1974 (39 FR 36008); February 25, 1977 (42 FR 10983); September 2,
1977 (42 FR 44230); November 8, 1977 (42 FR 58167); May 22, 1979 (44 FR
29653); August 24, 1979 (44 FR 49667); November 30, 1979 (44 FR 68822);
April 25, 1980 (45 FR 27927); August 31, 1984 (49 FR 34698); May 3,
1993 (58 FR 26386); May 19, 1994 (59 FR 26402); and July 2, 1999 (64 FR
35924)).
In the Federal Register of December 11, 1997 (62 FR 65235), FDA
issued an advance notice of proposed rulemaking requesting comments on
the proposed conceptual changes to the performance standard. The agency
received 12 comments from State and local radiation control agencies,
manufacturers, and a manufacturer organization. FDA considered these
comments in developing this proposal. In addition, the concepts
embodied in these proposed amendments were discussed on April 8, 1997,
during a public meeting of the Technical Electronic Product Radiation
Safety Standards Committee (TEPRSSC). TEPRSSC is a statutory advisory
committee (21 U.S.C. 360kk(f)(1)(A)) that FDA is required to consult
before it may prescribe any electronic product performance standard
under the act. The proposed amendments themselves were discussed in
detail with the TEPRSSC during its meeting on September 23 and 24,
1998. TEPRSSC approved the content of the proposed amendments and
concurred with their publication for public comment.
The proposed amendments described in section II of this document
may be considered as nine significant amendments to the current
standard and several other minor supporting changes, corrections, or
clarifications. The nine principal amendments fall into the following
three categories:
1. Amendments requiring changes to equipment design and performance;
2. Amendments designed to improve use of fluoroscopic systems by
requiring enhanced information to users; and
3. Amendments applying the standard to new features and technologies
associated with fluoroscopic systems.
II. Proposed Amendments to the Performance Standard for Diagnostic X-
Ray Systems and Their Major Components
A. Change in the Quantity Used to Describe X-Radiation From Exposure to
Air Kerma
FDA proposes to change the quantity and the associated unit used to
describe the radiation emitted by the x-ray tube or absorbed in air.
The radiation quantity ``exposure'' would be replaced by the quantity
``air kerma.'' The units used to describe these quantities would be
changed accordingly throughout the standard, wherever appropriate.
The International System of Units (SI) was named and adopted at the
11th General Conference on Weights and Measures (GCWM) in 1960 as an
extension of the earlier metric systems. The SI, also referred to as
the metric system, is the approved system of units for use in the
United States. The U.S. Department of Commerce published an
``Interpretation and Modification of the International System of Units
for the United States'' in the Federal Register on December 10, 1976,
which set forth the interpretation of the SI system for the United
States. The Omnibus Trade and Competitiveness Act of 1998 amended the
Metric Conversion Act of 1975 to require each Federal agency to use the
metric SI system in its activities. The FDA policy for use of metric
measurements is described in a March 19, 1990, memorandum. This policy
calls for use of the metric units followed by a parenthetic ``inch-
pound'' declaration unless there is a cogent reason not to utilize dual
metric and ``inch-pound'' measurements. The policy notes that there
should be few such exceptions.
One of the objectives of the International Commission on Radiation
Units and Measurements (ICRU) is to develop internationally accepted
recommendations regarding quantities and units of radiation and
radioactivity. The ICRU recommendations often form the basis of GCWM
actions. In 1998, the ICRU published its Report 60, ``Fundamental
Quantities and Units for Ionizing Radiation,'' superseding its previous
Report 33. Report 60 uses the SI units and special names for some
radiation units (Ref. 1). The ICRU had suggested phasing out by 1985
the use of certain special quantities and units that were not part of
the SI system, including the special unit of exposure, the roentgen
(R).
The current Federal performance standard for diagnostic x-ray
equipment uses the special quantity exposure to describe the radiation
emitted from an x-ray system. In the Federal Register of May 3, 1993
(59 FR 26386), FDA published a final rule which made a partial
transition to the SI units by changing the unit for exposure from
``roentgen'' (R) to ``coulomb per kilogram'' (C/kg). This change
required using an awkward conversion factor of 2.58 x 10-4
C/kg per R.
In view of current trends, scientific practice, the U.S. policy,
and FDA directives, FDA proposes that a complete conversion be made to
the SI quantities and units by amending the standard to require using
the quantity air kerma in place of the quantity exposure. Additionally,
the agency proposes that, in making this conversion, the absolute
magnitude of the limits on radiation contained in the standard not be
changed. This requires that the limits, when expressed in the new
quantity air kerma and its unit, the gray, be expressed with numerical
values different from the current limits that use the quantity
exposure.
In its recent reports, the National Council on Radiation Protection
and Measurement (NCRP) adopted the use of the SI quantity kerma, in
particular air kerma, to describe the radiation emitted from an x-ray
system. This change in the NCRP recommendations was made without
significant concern that previous limits in the voluntary
recommendations were slightly increased by this change when numerical
values for the limits were not changed but were expressed in the new
units. This change in the NCRP recommendations resulted in an increase
in the limits, compared to previous recommendations, of about 15
percent.
FDA is not proposing such an increase in this proposal. Instead,
FDA is proposing that the numerical values for limits in the standard
relating to radiation, when expressed in the new quantity, be changed
as well so the new limits will be equivalent to the current limits,
thereby making no change to the level of radiation protection provided
by the standard. FDA has dropped earlier draft proposals to change the
numerical values in a manner similar to the changes made to the
voluntary recommendations by the NCRP because of several comments that
were received. The comments objected to any changes to the level of
radiation protection provided by the limits in the current mandatory
standard.
This proposed approach to the numerical limits results in numerical
values that are not integer numbers or multiples of 5 or 10, as is the
case in the current standard, when limits are expressed in the non-SI
unit for
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exposure, roentgen. For example, the current limit for an exposure rate
of 10 R/minute (R/min), 2.58 x 10-3 C/kg per min, becomes an
air kerma rate (AKR) limit of 88 milligray per minute (mGy/min) under
the proposed approach.
FDA is proposing new definitions of the quantities kerma, as used
by the ICRU, and air kerma in Sec. 1020.30(b). Because the quantity
air kerma is a different quantity from exposure and not numerically
equivalent, FDA is proposing in the amended standard to express the
limits in terms of air kerma and indicate the equivalent limit in terms
of exposure using the word ``vice'' to indicate this equivalence. Thus,
the change described above would be given in the proposed amendments as
a limit expressed as ``88 mGy/min (vice 10 R/min)'' indicating that the
new limit of 88 mGy/min air kerma is equivalent to the previous limit
10 R/min exposure.
Current International Electrotechnical Commission (IEC) standards
for diagnostic x-ray systems use the quantity air kerma to describe the
radiation emitted by the x-ray system. The current limits on maximum
fluoroscopic exposure rates in the performance standard were
established to be consistent with the recommendation of the NCRP. The
proposed amendment maintains agreement between the performance standard
and the voluntary standards in terms of the quantities and units used.
But in order to maintain the current level of radiation protection and
in response to the comments received, the change results in numerical
limits for some of the requirements different from those used in the
current recommendations of the NCRP.
The term ``exposure'' is also used with a second meaning in the
performance standard that does not refer to a quantity of radiation as
defined here. The second meaning of ``exposure'' refers to the process
or condition during which the x-ray tube is activated by a flow of
current to the anode and radiation is produced. The second meaning of
exposure will continue to be used where appropriate. FDA is proposing
to revise the definition of the quantity exposure in Sec. 1020.30(b)
to match the current ICRU definition.
FDA also proposes in Sec. 1020.30(b) to amend the definitions of
``half-value layer'' (HVL) and ``x-ray field'' to reflect the change
from the quantity exposure to air kerma.
B. Clarification of Applicability of Requirements to Account for
Technological Developments in Fluoroscopic X-Ray Systems Such as
Digital Imaging, Digital Recording, and New Types of Solid-State X-Ray
Imaging Devices
When the performance standard was originally developed, the only
means for producing a fluoroscopic image was either a screen of
fluorescent material or an x-ray image intensifier tube. Thus, the
standard was originally written with these two types of image receptors
in mind. The advent of new types of image receptors, such as solid-
state x-ray imaging (SSXI) devices, and new modes of image recording,
such as digital recording to computer memory or other media, has made
the application of the current standard to systems incorporating these
new technologies cumbersome and awkward. These new aspects of
fluoroscopic system design have required a series of interpretations to
apply the standard appropriately. With this in mind, FDA proposes to
amend the performance standard to recognize these new types of image
receptors and modes of image recording and to clarify how the
requirements of the standard apply in each case. This amendment would
result in replacing the terms ``x-ray image intensifier'' or ``image
intensifier'' with the more general term ``fluoroscopic image
receptor'' in numerous sections.
Although the basic radiation protection and safety requirements for
fluoroscopic equipment in the performance standard are based on the
presence of an x-ray image intensifier, these requirements are also
appropriate for newer imaging systems that do not use an x-ray image
intensifier. The newer imaging systems may incorporate an image
receptor consisting of an absorbing material and an array of solid
state transducers that intercepts x-ray photons and directly converts
the photon energy into a modulated electrical signal. The signal often
goes through analog-to-digital conversion as part of the image
formation process to perform both fluoroscopy and radiography. FDA
proposes to modify the structure and organization of the standard to
address this new type of x-ray imaging equipment. The specific changes
proposed are described below in section II.C of this document.
For SSXI, new performance considerations are relevant because of
the different construction and the use of solid-state materials such as
silicon and selenium. These new considerations include: Changes in
spatial resolution, as quantified in the modulation transfer function
(MTF), dynamic range, and detective quantum efficiency; the
introduction of aliasing artifacts; reduced geometrical efficiency
(fill factor); and differences in the range of quantum-limited
operation when compared to the older vacuum-tube-based fluoroscopic
equipment. Because consensus is not available on some aspects of the
performance for these new devices, the agency has relied on premarket
review and associated guidance documents to provide the necessary
radiation safety control for these devices. (See, e.g., the ``Guidance
for the Submission of 510(k)s for Solid State X-Ray Imaging Devices ''
(Ref. 2).)
An example of a new performance consideration for the SSXI is the
active detector area. Because of the need for electrical separation/
insulation between individual detector elements, the detector area has
both active and inactive regions, in terms of detecting image
information. The relative areas of the active and inactive detector
areas are usually described in terms of the fill factor. The fill
factor, to a first approximation, is the pixel area (active area in
terms of image formation) times the number of pixels divided by the
total detector area exposed to the input image flux.
The fill factor and other characteristics can have significant
effects on imaging performance. The imaging performance must also be
considered when obtaining a complete picture of the effectiveness of
these devices. Although FDA is not offering specific proposals for
imaging performance at this time, FDA is inviting comment on possible
approaches to ensuring radiation protection and safety in the
application of these SSXI devices.
C. Changes and Additions to Definitions and Applicability Statements
To address the changes in technology and the new types of image
receptors and to allow these items to be appropriately integrated into
the standard, FDA proposes the following changes in definitions and
applicability sections of the standard. The changes in definitions
described here are in addition to those described above in section II.A
of this document.
First, in Sec. 1020.30(b), FDA proposes to amend the definition of
``fluoroscopic imaging assembly,'' ``image receptor,'' ``spot-film
device,'' and ``x-ray table'' by removing the reference to an x-ray
image intensifier as the descriptor of the image receptor or by
replacing image intensifier with the more general term fluoroscopic
image receptor.
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Second, FDA also proposes in Sec. 1020.30(b) to amend the
definition of the term ``recording'' by removing the word ``permanent''
and replacing it with the word ``retrievable,'' and to remove the
examples of ``recording,'' to clarify the definition of the term
``recording'' in the context of images stored on recording media other
than film.
Third, in Sec. 1020.30(b), FDA proposes to clarify the
applicability of the standard or to bring precision to the meaning of
specific requirements by adding definitions for the terms solid state
x-ray imaging device, fluoroscopy, radiography, non-image intensified
fluoroscopy, automatic exposure rate control, isocenter, last image
hold (LIH) radiograph, mode of operation, and source-skin distance
(SSD).
Last, under Sec. 1020.30(b), FDA proposes to add a definition of
``lateral fluoroscope'' to clarify the distinction between a lateral
fluoroscope and what is commonly referred to as a C-arm fluoroscope. In
an August 29, 1977, Compliance Policy Guide, FDA described the geometry
for measuring, during a compliance test, the entrance exposure rate for
lateral fluoroscopes. The standard does not define a system by the way
it is used but allows the manufacturer to specify the use for which the
equipment is designed. The design of the system determines whether the
system is a C-arm or a lateral fluoroscope. If the system is a C-arm,
it is tested using the test geometry for a C-arm system, even if it is
used with a lateral beam direction. If the system is a dedicated
lateral fluoroscope used with a biplane system, the more restrictive
measurement geometry, as described for a lateral fluoroscope in the
current Sec. 1020.32(d)(4)(iv) and (e)(3)(iv), will be used. This test
geometry is described in proposed Sec. 1020.32(d)(3)(v).
The lateral fluoroscope consists of a support structure holding a
tube housing assembly and a fluoroscopic imaging assembly with the x-
ray beam in a lateral projection parallel to the plane of the tabletop.
Thus, the geometry of the source and image receptor is fixed relative
to the patient or x-ray table. The entrance air kerma would be measured
with the radiation measurement instrument detector placed 15
centimeters (cm) from the center of the table in the direction toward
the x-ray source. (This position is considered to be typical of the
entrance skin surface of the patient.) During the measurement, the tube
housing assembly is positioned as close to this location as allowed by
the system. For C-arm system measurement geometry, the patient is
assumed to be as close to the image receptor as possible and,
therefore, the detector is placed 30 cm from the entrance surface of
the image receptor. In a lateral fluoroscope, the patient cannot be
placed against the image receptor, and the measurement point is
referenced to the center of the table. The standard does not require
that the table have the centerline indicated. Testing is performed
relative to the centerline and the center is located by measurement if
necessary.
Additionally, FDA proposes to correct two minor typographical
errors that were introduced into the definitions of ``leakage technique
factors'' and ``spot-film device'' in the May 3, 1993, Federal
Register.
FDA proposes in Sec. Sec. 1020.31 and 1020.32 to amend the
applicability statements by removing the reference to an x-ray image
intensifier as the descriptor of the image receptor used to distinguish
between radiography and fluoroscopy. FDA proposes to further modify the
applicability statements to clearly identify the type of x-ray imaging
equipment to which each section applies and to distinguish between
radiographic and fluoroscopic imaging.
Additionally, to complete the transition to the use of the
terminology ``fluoroscopic image receptor,'' FDA proposes in Sec.
1020.32(a)(1) and (a)(2), to replace the term ``image intensifier''
with the more inclusive term ``fluoroscopic image receptor'' to reflect
the changes in fluoroscopic image receptor technology and design. This
change will, therefore, include SSXI devices, x-ray image intensifiers,
and other fluoroscopic image receptors within the transmission limit
and measurement criteria of paragraphs (a)(1) and (a)(2).
Similarly, FDA proposes in Sec. 1020.32(g) to remove ``image-
intensified fluoroscope'' and add in its place the generic term
``fluoroscope'' in the description of the requirement for minimum SSD
for systems intended for specific surgical applications.
Finally, in Sec. 1020.32(i), FDA proposes to remove the term
``intensified imaging'' and add in its place ``image receptor
incorporating more than a simple fluorescent screen.'' This removes the
reference to a specific type of fluoroscopic image receptor, the image
intensifier, and includes all types of receptors other than a simple
fluorescent screen as meeting the requirement of Sec. 1020.32(i).
D. Information to be Provided to Users (Sec. 1020.30(h))
FDA proposes to add two paragraphs to Sec. 1020.30(h). Proposed
Sec. 1020.30(h)(5) and (h)(6) would require manufacturers to provide
in the instructions for users additional information regarding
fluoroscopic x-ray systems.
Recent developments in the technology of fluoroscopic systems have
resulted in equipment being increasingly provided with a variety of
special modes of operation and methods of recording fluoroscopic
images. Some of these modes of operation may significantly increase the
entrance AKR to the patient compared to conventional fluoroscopy. There
is concern that the operating instructions provided with the
fluoroscopic system lack sufficient information concerning the
characteristics of these special modes of operation to permit the
operator to adequately evaluate the increased radiation output and
consequent increased exposure to the patient and operator from these
modes of operation. There is typically little information provided to
users on the clinical procedure(s) for which each mode was designed,
resulting in potential inappropriate application of the mode by a user
who is not fully aware of the intended application of the particular
mode of operation.
Proposed Sec. 1020.30(h)(5) would require that the information
provided to users contain a detailed description of each mode of
operation and specific instructions on the manner in which the mode is
engaged or disengaged. The manufacturer would also be required to
provide information on the specific types of clinical procedures or
imaging tasks for which the mode is intended and instructions on how
each mode should be used. This information is to be provided in a
special section of the user's instruction manual or in a separate
manual devoted to this purpose.
Section 1020.30(h)(1)(i) of the performance standard states that
the information to users shall contain ``Adequate instructions
concerning any radiological safety procedures and precautions which may
be necessary because of unique features of the equipment * * *.'' FDA
considers any mode of operation that yields an entrance AKR above 88
mGy/min to be a unique feature of the specific fluoroscopic equipment
and thus must have a full and complete description in the instructions
for its use.
FDA is also of the opinion that, for modes of operation where the
entrance
[[Page 76060]]
AKR exceeds 88 mGy/min, the manufacturer should provide detailed
information to permit the user to assess the exposure to the patient
relative to that delivered in the normal mode of operation. Such
information would give operators important radiation safety data with
which to make better judgments on the possible hazards involved with a
particular procedure. FDA has learned that, because of the multiple
number of modes and options available with many of the systems, many
users are not aware of when or how such modes are engaged and
disengaged or the radiation output consequences of such modes. FDA had
originally considered requiring the manufacturer to provide data on the
entrance AKRs for each mode of operation of the fluoroscopic system.
However, the large number of possible combinations of modes and options
for operation available with many of the systems makes this
impractical. The proposed amendment described in section II.J of this
document would require the manufacturer to provide a display of the AKR
and cumulative air kerma. With this information, the user is made aware
of the relative changes in the AKR when changing from one mode of
operation to another. Awareness of such changes will inform the user of
the relative output changes of the system as a function of mode of
operation, patient size, and system geometry.
FDA believes that manufacturers are already providing much of the
information proposed in this requirement. However, the information may
not be displayed in a separate section of the manual where users can
readily find it, and the information may not contain enough detailed
information on the intended use of the various modes of operation to
assure proper use of the system.
Proposed Sec. 1020.30(h)(6) would require manufacturers to provide
users with information regarding the new features of fluoroscopic
systems described in proposed Sec. 1020.32(k). Proposed Sec.
1020.30(h)(6) would also require manufacturers to provide information
regarding the display of values of AKR and cumulative air kerma. This
information will include a statement of the maximum deviation of the
actual values of AKR and cumulative air kerma from their displayed
values, maintenance and instrumentation calibration information, and a
description of the spatial coordinates of the reference location for
which the displayed values are given.
E. Increase in Minimum Half-Value Layer (Sec. 1020.30(m)(1))
FDA proposes to modify the requirement for minimum HVL to recognize
changes in x-ray tube and x-ray generator technology over the last few
decades.
The use of x-ray filtration to increase the quality or homogeneity
of an x-ray beam through selective absorption of the low energy photons
has been a recommended practice for a long time. A 1968 report
published by NCRP (appendix B, table 3, in Ref. 3) provides the beam
quality in terms of HVL, as a function of tube potential, that would
result from specified values of total x-ray filtration in the x-ray
beam. However, the values of HVL in the table would only result if one
used the NCRP suggested values of total filtration in diagnostic x-ray
equipment of that era (i.e., the 1960s to early 1970s). It should be
noted that diagnostic x-ray equipment of that era was characterized by
x-ray tubes with a large x-ray target angle and x-ray generators with
significant ripple in the high voltage waveform (e.g., an x-ray target
angle of 22[deg] and a high voltage ripple of 25 percent).
The requirements on beam quality in the current IEC international
standard (Ref. 4) are also expressed in a similar manner as the NCRP
Report No. 33 (i.e., a total filtration requirement plus a set of
minimum HVL values). The Institute of Physical Sciences in Medicine has
recently published a report which can be used to estimate the total
filtration from HVL data as a function of x-ray target angle and high
voltage ripple (Ref. 5). These data point out the lack of
correspondence between a total filtration of 2.5 millimeters (mm) of
aluminum and the minimum HVL requirements in the performance standard
for state-of-the-art x-ray equipment (e.g., an x-ray target angle of
12[deg] and a high voltage ripple of 10 percent). For these types of
equipment, the minimum HVL requirements in the performance standard can
be met with about 1.8 mm of total filtration versus the required 2.5 mm
of total filtration as specified in the IEC standard (Ref. 4). Only
equipment with large x-ray target angles (22[deg]) and a great deal of
high voltage ripple (25 percent) need a total filtration of 2.5 mm of
aluminum to meet the minimum HVL requirements in the performance
standard. In terms of skin-sparing effect, the performance-oriented set
of minimum HVL values in the performance standard have not kept up with
changes in x-ray equipment when compared to the design-oriented
requirement of a total filtration of 2.5 mm of aluminum.
For these reasons, FDA proposes to increase the minimum HVL values
for radiographic and fluoroscopic equipment excluding mammography
equipment and dental equipment designed for use with intraoral image
receptors. The proposed minimum HVL values represent the values
obtained with a total filtration of 2.5 mm of aluminum on state-of-the-
art diagnostic x-ray equipment (i.e., an x-ray target angle of 12[deg]
and a high voltage ripple of 10 percent). FDA used the data in the
Institute of Physical Sciences in Medicine report to arrive at the
proposed minimum HVL values.
As a separate x-ray filtration issue, there has been a substantial
increase over the past 20 years in the use of x-ray fluoroscopy as a
visualization tool for a wide range of diagnostic and therapeutic
procedures. Because of the long catheter manipulation times and the
need, in some cases, for a stationary x-ray field, these procedures
have the potential, sometimes realized, for high radiation dose to
patients and clinical personnel (Ref. 6). In fact, the agency has been
actively involved in promoting recommendations for the avoidance of
serious, x-ray-induced, skin injuries to patients during
fluoroscopically-guided interventional procedures. As a result, there
continues to be an interest in dose reduction techniques for these
procedures.
In general, the addition of either beam-hardening or K-edge x-ray
filters can provide a significant reduction in the exposure,
particularly skin exposure, to the patient. However, this reduction in
exposure is accompanied by an attendant increase in tube load (Ref. 7).
It should be noted that one of the recommendations of the work group on
the technical aspects of fluoroscopy at the 1992 American College of
Radiology (ACR)/FDA workshop on fluoroscopy (Ref. 8) was to increase
the minimum HVL. Therefore, FDA is also proposing an additional
requirement for fluoroscopic x-ray systems incorporating x-ray tubes of
high heat-load capacity. Manufacturers of these systems would be
required to provide a means, at the user's option, for adding
additional x-ray filtration over and above the amount needed to meet
the proposed new minimum HVL values. This requirement is based on the
assumption that x-ray tubes with high heat-load capacity are typically
required or provided on equipment designed for use in interventional
procedures due to the imaging task requirements and the extended
exposure times associated with interventional procedures. The
[[Page 76061]]
method of implementation and the actual values of additional filtration
to realize the reduction in skin exposure will be left to the
discretion of the manufacturer.
F. Change in the Requirement for Fluoroscopic X-Ray Field Limitation
and Alignment (Sec. 1020.32(b))
FDA proposes to reorganize and add new paragraphs to Sec.
1020.32(b) to require improved x-ray field limitation for fluoroscopic
x-ray systems. Section 1020.32(b) would be reorganized to retain the
current requirements applicable to systems manufactured before the
effective date of these amendments. For systems manufactured after the
effective date, new requirements are proposed in Sec. 1020.32(b)(4)
and (b)(5) respectively, for systems with inherently circular or
rectangular image receptors. These proposed new requirements will
result in increased geometric efficiency or more efficient use of
radiation as described below.
The proposed reorganization and retention of the existing
requirements in Sec. 1020.32(b) will be accomplished in the following
manner: Section 1020.32(b)(1)(i) will be redesignated as Sec.
1020.32(b)(3); Sec. 1020.32(b)(1)(ii) and (b)(2)(iii) will be combined
and redesignated as Sec. 1020.32(b)(1) with appropriate revisions to
paragraph references to reflect the reorganization of Sec. 1020.32(b);
Sec. 1020.32(b)(2)(iv) will be redesignated as Sec. 1020.32(b)(2)
with a minor clarification; and Sec. 1020.32(b)(3) will be moved and
redesignated as new Sec. 1020.32(b)(6). Additionally, Sec.
1020.32(b)(2)(i) and (b)(2)(ii) will be moved to Sec. 1020.32(b)(4)(i)
as Sec. 1020.32(b)(4)(i)(A) and (b)(4)(i)(B).
New requirements of improved efficiency for systems manufactured
after the effective date of the amendments are proposed in Sec.
1020.32(b)(4)(ii) for systems with inherently circular image receptors.
Section 1020.32(b)(5) would contain the field limitation requirements
for systems with inherently rectangular image receptors. The
requirements proposed for systems with rectangular image receptors are
the same as those currently applicable to radiographic systems provided
with positive beam limitation or to spot-film devices that utilize
rectangular image receptors. As such, the proposed tolerances for x-ray
field limitation are considered technically feasible.
A reduction in unnecessary patient exposure is the basis for all of
the x-ray field limitation and alignment requirements in the
performance standard. For example, any radiation falling outside the
visible area of the image receptor provides no useful diagnostic or
visualization information and, therefore, represents unnecessary
patient exposure. Once it is recognized that restricting the size of
the x-ray field provides an effective control of unnecessary radiation
exposure, the question shifts to what is the tolerance technically
achievable by the manufacturer for the matching of the x-ray field and
the visible area of the image receptor.
The current performance standard (Sec. 1020.32(b)(2)(i)), states
``neither the length nor the width of the x-ray field in the plane of
the image receptor shall exceed that of the visible area of the image
receptor by more than 3 percent of the SID. The sum of the excess
length and the excess width shall be no greater than 4 percent of the
SID.'' These requirements result in worst-case values of geometrical
efficiency enumerated in table 1 of this document for what are typical
geometrical and operating conditions on fluoroscopic systems.
Geometrical efficiency is defined as the ratio of the visible area
divided by the area of the x-ray field. It should be noted that the
requirements in the existing IEC international standard with respect to
x-ray field limitation are more stringent than in the performance
standard (Ref. 4). When the x-ray field is rectangular and the visible
area is circular, the IEC standard requires that the length and width
of the x-ray field be less than the diameter of the maximum visible
area of the image intensifier. Thus, if the x-ray field is centered on
the visible area of the image intensifier, the x-ray field would exceed
the visible area of the image intensifier only in the corners of a
rectangular x-ray field, unlike what could result from following the
current performance standard.
Table 1.--Worst-Case Geometrical Efficiency in Percentage for a
Fluoroscopic System\1\
------------------------------------------------------------------------
Visible Area (circular, X-Ray Field (worst
cm\2\) case, square, cm\2\) Efficiency (%)
------------------------------------------------------------------------
113 196 57
------------------------------------------------------------------------
177 289 61
------------------------------------------------------------------------
415 625 66
------------------------------------------------------------------------
707 1,024 69
------------------------------------------------------------------------
\1\ Worst-Case Geometrical Efficiency in Percentage for a Fluoroscopic
System With a Source-Image Receptor Distance (SID) of 100 cm, a Square
X-Ray Field Size at the Limits Allowed by Sec. 1020.32(b)(2)(i), and
Image Intensifiers With 12-, 15-, 23-, and 30-cm Diameter Visible
Areas.
As can be seen from table 1 above, the current performance standard
allows the possibility of relatively low geometrical efficiency,
particularly in modes of operation corresponding to small visible areas
on the image intensifier. It should be noted that many
fluoroscopically-guided interventional procedures involve the use of
small visible areas on the image intensifier (Ref. 9). These low values
of geometrical efficiency are a direct result of using a square
collimator for the x-ray field when faced with an inherently circular
visible area for the image receptor. The use of a continuously
adjustable, circular collimator and/or circular apertures along with
adjustable rectangular collimation would increase the geometrical
efficiency.
Many currently marketed x-ray systems suitable for
fluoroscopically-guided interventional procedures provide continuously
adjustable, circular collimators as a basic and/or optional capability
(Ref. 10). Thus, a continuously adjustable, circular collimator is
technically feasible, albeit at some additional cost to the user
community. Fluoroscopic x-ray systems with this feature can provide a
substantial increase in geometrical efficiency that is important for
all types of radiological procedures but particularly important for
interventional procedures resulting in high skin exposure.
It is for these reasons that FDA proposes to require geometrical
efficiencies of 80 percent or more for all fluoroscopic x-ray systems.
When the visible area of the image receptor is
[[Page 76062]]
greater than 34 cm in any direction, a geometrical efficiency of 80
percent is no longer sufficiently stringent. FDA proposes to change the
requirement to a sizing tolerance at that point (i.e., the x-ray field
measured along the direction of greatest misalignment with the visible
area of the image receptor shall not extend beyond the visible area of
the image receptor by more than 2 cm). This oversizing tolerance will
ensure geometrical efficiencies of better than 80 percent for large
image receptors. In those unusual cases where the x-ray field is not
uniformly intense over its cross-section, the proposed field limitation
and alignment requirement provides for measurement of efficiency in
terms of air kerma integrated over the x-ray field incident on the
visible area of the image receptor (Ref. 11).
The intent is to promote the incorporation of continuously
adjustable, circular collimators into all types of fluoroscopic x-ray
systems with circular image receptors. FDA acknowledges that the new
requirements could be met through the use of less complex, currently
available, rectangular collimation and underframing. For example, the
amount of underframing (defined as the difference in the width of the
x-ray field versus the diameter of the visible area) of a rectangular
x-ray field needed to meet the new requirements is enumerated in table
2 of this document for the same geometrical and operating conditions of
fluoroscopic systems described in table 1 of this document. The agency
is soliciting comments on the ramifications of this amount of
underframing. These proposed requirements for increased x-ray
utilization efficiency would appear in proposed Sec. 1020.32(b)(4)(ii)
for systems manufactured after the effective date of the amendments.
Table 2.--Underframing of a Rectangular X-Ray Field\1\
------------------------------------------------------------------------
X-Ray Field Width
Visible Area Diameter (cm) (cm) Underframing (cm)
------------------------------------------------------------------------
12 11.9 -0.1
------------------------------------------------------------------------
15 14.9 -0.1
------------------------------------------------------------------------
23 22.8 -0.2
------------------------------------------------------------------------
30 29.7 -0.3
------------------------------------------------------------------------
\1\ Amount of Underframing of a Rectangular X-Ray Field Needed to Meet
the New Field Limitation Requirements for a Fluoroscopic System With
an SID of 100 cm and Image Intensifiers With 12-, 15-, 23-, and 30-cm
Diameter Visible Areas.
Although the field limitation requirements for fluoroscopic
equipment in the performance standard are predicated on the presence of
an x-ray image intensifier, the requirements are also appropriate for
newer imaging systems that do not use an x-ray image intensifier. As
mentioned previously, the newer imaging systems may incorporate an
image receptor consisting of an absorbing material backed by an array
of solid state transducers that intercepts x-ray photons and converts
the photon energy into a modulated electrical signal with eventual
analog-to-digital conversion. These image receptors are inherently
rectangular. As is the case for image intensifier based systems,
magnification modes are available through the use of a ``digital zoom''
where only a selected portion of the digital array is visible to the
operator. FDA is proposing to apply the current requirements of the
standard for x-ray field limitation that are used for spot-film devices
or radiographic systems equipped with positive beam limitation, and
which also use rectangular fields, to this new type of image receptor.
These requirements result in worst-case values of geometrical
efficiency (defined as the square visible area divided by the area of a
square x-ray field) enumerated in table 3 of this document for what are
typical geometrical and operating conditions of fluoroscopic systems.
Table 3.--Worst-Case Geometrical Efficiency in Percentage for a
Fluoroscopic System\1\
------------------------------------------------------------------------
Visible Area Diameter X-Ray Field (square,
(square, cm\2\) cm\2\) Efficiency (%)
------------------------------------------------------------------------
144 196 73
------------------------------------------------------------------------
225 289 78
------------------------------------------------------------------------
529 625 85
------------------------------------------------------------------------
900 1,024 88
------------------------------------------------------------------------
\1\ Worst-Case Geometrical Efficiency in Percentage for a Fluoroscopic
System With an SID of 100 cm, a Square X-Ray Field Size at the Limits
Allowed by Sec. 1020.32(b)(2)(i), and Solid-State X-Ray Images with
12 cm x 12 cm, 15 cm x 15 cm, 23 cm x 23 cm, and 30 cm x 30 cm Visible
Areas.
As can be seen from table 3 above, the current standard provides
relatively high geometrical efficiency. In this case, the high values
of geometrical efficiency are a direct result of using a rectangular
collimator for the x-ray field when faced with an inherently
rectangular visible area for the image receptor. Proposed Sec.
1020.32(b)(5) would explicitly state the field limitation requirements
for systems with inherently rectangular image receptors.
G. Revisions and Change in the Limits to Maximum Air Kerma Rate (Sec.
1020.32(d) and (e))
In Sec. 1020.32, FDA proposes to revise and reorganize Sec.
1020.32(d) and (e) to clarify and simplify the requirements on maximum
AKR for fluoroscopic x-ray systems. In Sec. 1020.32(d), FDA proposes
to incorporate all of the requirements for AKR limits regardless of the
date of manufacture of the x-ray system. The revised paragraph would
also incorporate the new quantity kerma and the corresponding limits on
entrance
[[Page 76063]]
AKRs. FDA proposes to move the current requirements of Sec. 1020.32(e)
that are applicable to equipment manufactured on or after May 19, 1995,
to the revised Sec. 1020.32(d). This would consolidate all of the
requirements for limits on the maximum AKR in a single section (i.e.,
revised Sec. 1020.32(d)). Section 1020.32(e) would be reserved.
The requirements applicable to fluoroscopic systems manufactured
before May 19, 1995, currently contained in Sec. 1020.32(d)(1) through
(d)(3), would be contained in revised Sec. 1020.32(d)(1). No change in
the limit on maximum AKR for previously manufactured fluoroscopic
systems is introduced by the reorganization and simplification of
current Sec. 1020.32(d). This simplification is obtained by describing
the exceptions to the maximum AKR only one time in proposed Sec.
1020.32(d)(1)(v) rather than three times as in current Sec.
1020.32(d)(1) through (d)(3).
Proposed Sec. 1020.32(d)(1) also includes Sec. 1020.32(d)(1)(iv)
that makes explicit the fact that systems manufactured before May 19,
1995, may be modified to comply with new requirements contained in
proposed Sec. 1020.32(d)(2). The rationale for this addition is
described in section II.M of this document.
Proposed Sec. 1020.32(d)(2) would include the requirements
applicable to fluoroscopic systems manufactured on or after May 19,
1995. Section 1020.32(d)(2)(i) would contain the language currently in
Sec. 1020.32(e)(1) that requires systems with the capability for AKR
greater than 44 mGy/min to be provided with automatic exposure rate
control.
Section 1020.32(d)(2)(ii) would contain the requirements of current
Sec. 1020.32(e)(2) that became effective on May 19, 1995, and
establish an upper limit on the AKR during high-level control mode of
operation. Section 1020.32(d)(2)(iii) would incorporate the exceptions
to the maximum AKR limit given in Sec. 1020.32(d)(2)(ii). Section
1020.32(d)(2)(ii)(A) would contain the exception currently found in
Sec. 1020.32(e)(2)(i) that addresses the recording of images using a
pulsed mode applicable to equipment manufactured prior to the effective
date of these amendments. For equipment manufactured after the
effective date of these amendments, Sec. 1020.32(d)(2)(ii)(B) would
add an additional new exception described below in section II.H of this
document. Finally, the exception currently found in Sec.
1020.32(e)(2)(ii) addressing high-level control mode of operation would
be moved to Sec. 1020.32(d)(2)(ii)(C).
The conditions under which compliance is determined are currently
found in Sec. 1020.32(d)(4) and (e)(3). These conditions would be
moved to Sec. 1020.32(d)(3). Section 1020.32(d)(3)(vi) would be added
to specifically address the measurement conditions for systems with
SIDs less than 45 cm. For these systems, FDA is proposing that
compliance be determined by measurement at the minimum SSD.
The exemption for radiation therapy simulation systems currently
found in Sec. 1020.32(d)(5) and (e)(4) would be incorporated into a
proposed revision of Sec. 1020.32(d)(4).
H. New Modes of Image Recording
New requirements would be established in a Sec.
1020.32(d)(2)(iii)(B) to further limit the conditions under which the
limit on the maximum AKR rate would not apply. In May 1994, the agency
amended the requirements in the standard pertaining to the limit on
entrance exposure rate (EER) during fluoroscopy. (For convenience in
discussing the current standard and proposed changes, reference will be
made to the limits on EER rather than to entrance AKR which will be the
quantity used in the amended standard.)
These 1994 amendments prescribed an exception to the limit on EER
during the recording of images ``from an x-ray image intensifier tube
using photographic film or a video camera when the x-ray source is
operated in a pulsed mode.'' (Pulsed mode is defined as operation of
the x-ray system such that the x-ray tube current is pulsed by the x-
ray control to produce one or more exposure intervals of duration less
than one-half second.) These amendments also prescribed a limit on EER
of 20 R/min when an optional high-level control was activated during
fluoroscopy.
The basic premise of these amendments was to provide for a set of
limits on the maximum EER during fluoroscopy, and for an exception
during radiographic modes of operation such as cine-radiography. The
defining terms for determining whether the equipment was in fluoroscopy
versus radiography mode of operation were ``recording of images'' and
``pulsed mode.'' In retrospect, these terms were not explicit enough
for making a determination of the mode of operation. For example, the
current wording would allow adding a recording device such as a video
tape recorder to the imaging chain in a pulsed mode of operation. This
would, thereby, circumvent the intent of the regulation and allow the
limit on maximum EER during fluoroscopy to be exceeded, even though the
recorded images are never used in the radiological examination and are
used only for archiving purposes, if used at all.
As mentioned in the earlier discussion on new types of image
receptors, FDA is proposing new definitions for fluoroscopy and
radiography. These definitions are needed to make a clearer distinction
between fluoroscopy and radiography, regardless of the type of image
receptor being used. A key element in the new definitions is that
radiographic images recorded from the fluoroscopic image receptor must
be available for viewing after the acquisition of the images and during
or after the procedure, whereas fluoroscopic images are viewed in real
time, or near-real time during the procedure. Thus, the definitions of
the two modes of operation, i.e., radiography and fluoroscopy, are tied
to the intended use, and not to an arbitrary interval of time, as under
the current ``pulsed mode'' definition.
In addition to the proposed new definitions, FDA proposes to change
the description of the conditions under which exceptions to the limit
on maximum AKR are allowed. Section 1020.32(d)(2(iii) would contain two
exemptions. The exemption currently in Sec. 1020.32(e)(2)(i) would be
moved to Sec. 1020.32(d)(2)(iii)(A) and would apply to fluoroscopic
systems manufactured on or after May 19, 1995, but before the effective
date of the proposed amendment. A new exception would be added in Sec.
1020.32(d)(2)(iii)(B). This exception would recognize that image
receptors other than x-ray image intensifiers tubes are now used in
fluoroscopy and would remove the reference to operation in a pulsed
mode. Instead, the exception to the limit on maximum AKR would apply to
any recording of images from the fluoroscopic image receptor except
when the recording of images is accomplished using a video tape
recorder or a video disk recorder. This would prevent the simple
addition of an analog image-recording device to the fluoroscopic system
as a means to overcome the limit on maximum AKR during normal
fluoroscopy.
As discussed in the preamble of the proposed 1993 amendments (58 FR
26407, May 3, 1993), the agency is still interested in receiving
information on any clinical situations that could require higher AKR
than currently permitted. Such situations have been suggested to arise
due to the necessity of momentarily viewing the patient or the state of
a device in a patient as best as can be done or with the highest image
quality obtainable during fluoroscopy
[[Page 76064]]
mode of operation. Some anecdotal evidence seems to argue for an
increase in the EER above the current 20 R/min limit under high-level
control. The 1994 change in the regulations underwent an extensive
review and comment period. The consensus of that review, although not
unanimous at the time of issuance of the regulations, was that 20 R/min
would be sufficiently high for most clinical fluoroscopy situations.
The agency was and is still sensitive to the concern that the limits on
EER may in some cases compromise the clinical utility of the
fluoroscopic equipment.
Because of these concerns regarding the appropriate upper limit
AKR, FDA is encouraging further comment on the topic of limits on AKR
under normal and high-level fluoroscopy modes. For example, some
members of the radiological community have proposed that fluoroscopic
equipment allow a momentary viewing of the state of an intervention at
an increased but unspecified AKR. This momentary view would have a
maximum duration of 10 to 15 seconds. This proposal was accompanied
with the comment that if physicians are not allowed to use such a mode,
they will continue the practice of using cineradiography bursts at high
AKRs to accomplish the clinical task.
I. Entrance Air Kerma Rate at the Fluoroscopic Image Receptor
Comments received by the agency suggest that an alternative
approach in place of or in addition to limits on AKR during fluoroscopy
would be more useful and effective in limiting unnecessary radiation
and assuring optimum system performance. The suggestion is that the
limits on AKR to the patient (represented by a measurement made
according to the compliance geometry described in current Sec.
1020.32(e)(3)) be replaced by limits on the entrance AKR at the input
surface of the image receptor (EAKIR). Different EAKIR limits could be
established for different modes of fluoroscopic imaging, depending on
the image performance required for the clinical task.
There is a precedent for this approach in other consensus documents
such as the NCRP Report No. 99 and NCRP Report No. 102 (Refs. 12 and
13). For example, the NCRP Report No. 99 states that during fluoroscopy
``typical image intensifier entrance exposure should be in the range of
13 to 52 nC/kg/image (50 to 200 microR/image) depending on image
intensifier size * * *.'' (Note that, in the opinion of FDA, there is
an error in the NCRP Report No. 99: these numbers reflect exposure per
second, not exposure per image.) In the same manner, the NCRP Report
No. 102 provides a table with ``air kerma rate values to produce
acceptable fluoroscopy images'' and ``air kerma to produce static
images equivalent to that produced by a par speed screen-film system.''
FDA invites comments on the feasibility and desirability of this
approach to limit unnecessary radiation from fluoroscopic systems.
J. Requirement for Minimum Source-Skin Distance for Small C-Arm
Fluoroscopic Systems (Sec. 1020.32(g))
FDA proposes in Sec. 1020.32(g) to add Sec. 1020.32(g)(2) to
establish a minimum source-skin distance (MSSD) for ``C-arm'' type x-
ray systems having source-to-image-receptor distances of 45 cm or less
and intended for imaging extremities. This amendment would incorporate
into the performance standard the content of variances from the
performance standard granted according to Sec. 1010.4.
FDA has granted variances from the requirement set out in
Sec. 1020.32(g) for a limit on the MSSD for fluoroscopic x-ray systems
that were designed as small portable C-arm systems. These are
fluoroscopic systems that were originally designed to be hand-held and
were used at sporting events for a quick examination/diagnosis of
orthopedic injuries. In fact, some of the early systems used a
radioisotope instead of an x-ray tube as the source of the radiation
and were, therefore, outside the purview of FDA under the RCHSA
(although they are regulated as medical devices). Over time,
manufacturers of these devices enlarged the distance or opening between
the x-ray source and the image receptor to allow examination of larger
extremities. The argument was that some athletes had larger extremities
and a larger opening was needed to permit the use of the systems on
them. The systems were marketed under a variance from Sec. 1020.32(g)
and were labeled for extremity use only. As the size of the opening on
systems for which variances have been requested has increased from
about 20 cm to 35 cm, and manufacturers have increased the radiation
output of these systems, the agency has become concerned about the loss
of the skin-dose sparing properties of the MSSD requirement. In
addition, because a variance is granted for a finite time period,
renewal of the variances and the reviewing of new conditions for use
present resource implications for FDA and the manufacturers.
The justification for a variance from Sec. 1020.32(g) used by many
manufacturers of these small C-arm systems is geometrical scaling.
Manufacturers have stated in their variance applications that the MSSD
is proportional to the source-image receptor distance in comparison to
full-sized C-arm systems. Although extremities can be considered to
scale geometrically in a similar manner compared to the trunk or large
body parts, other body parts do not scale in such a manner as to
maintain a similar skin dose. For the source-image receptor distances
used in these systems, evaluation of this geometrical relationship
shows that the factor, by which the entrance AKR to the body part
increases over that for thinner parts, increases significantly as the
thickness of the body part being imaged reaches over 15 or 16 cm. This
increase reaches a factor of two for a thickness of 26 cm and increases
rapidly for thicker parts. In their original configuration, these
devices had a very small opening and could not accommodate anything
other than a limb. The latest configurations can easily accommodate the
whole body of a neonate or a pediatric patient.
At some point, these systems no longer represent small C-arms for
extremity use alone but are simply slightly smaller versions of
conventional C-arms for whole-body, general-purpose examinations. If
the system can be used for whole-body examination purposes, it should
meet the minimum radiation safety standards applicable to conventional
C-arm systems. Through the variance petition process, FDA has limited
the small C-arm systems to extremity use only.
To incorporate the protection provided by the conditions imposed by
the variances and to incorporate this requirement in the performance
standard, FDA proposes to limit the source-skin distance to not less
than 19 cm for fluoroscopic systems having source-image receptor
distances of 45 cm or less. Provision would be allowed for systems
designed for specific surgical applications to be operated with a
source-skin distance of not less than 10 cm. Systems subject to this
requirement would be required to be labeled for use for imaging
extremities only. Manufacturers would be required to include
appropriate precautions in the information provided to users under
Sec. 1020.30(h).
K. Requirements for Display of Fluoroscopic Irradiation Time, Air Kerma
Rate, and Cumulative Air Kerma (Sec. 1020.32(h) and Proposed (k))
FDA is proposing that newly manufactured fluoroscopic systems
display directly to the fluoroscopist information related to three
[[Page 76065]]
fundamental aspects of patient irradiation--the duration, rate, and
amount of x-ray emissions. Generally, fluoroscopic systems do not
currently provide such information at all. Irradiation time, AKR, and
cumulative air kerma are basic radiological variables important for
medical radiation protection. Their values may be applied to the
process of optimization (i.e., obtaining radiological images with the
least amount of radiation required), to the assessment of radiation
detriment as a factor affecting patient-outcome efficacy, and to the
development of reference levels representative of normal clinical
practice. Optimization, efficacy, and reference levels currently
comprise a conceptual vanguard of radiation protection in medicine at
the international level (Refs. 14 to 17). When monitored in the clinic,
irradiation time, AKR, and cumulative air kerma may be used to indicate
risk of acute skin injury arising from potentially prolonged
irradiation associated with some interventional procedures (Refs. 18 to
20). Values displayed directly to practitioners as an examination or
procedure progresses can feed back to them indices of radiation burden,
and practitioners can respond promptly by adjusting protocols and
techniques to minimize dose to patients and practitioners as
practitioners optimize radiation levels necessary for medical imaging.
Moreover, for fluoroscopy and radiography in general, knowledge of
irradiation levels at patient skin entrance is an essential starting
place for evaluation of absorbed dose to internal tissues (Refs. 9 and
21). Such doses are stochastically linked to cancer morbidity,
mortality, and to genetically transmissible defects (Refs. 14 and 22).
Estimates of cumulative doses absorbed in tissues foster risk
communication between medical staff and patients and, when tracked over
time, are effective indicators of practice consistency, variability, or
anomaly in the quality assurance activities associated with assuring
the safety of clinical procedures.
The need for displays of irradiation variables was recognized at
the 1992 national workshop on safety issues in fluoroscopy organized by
the ACR and FDA (Ref. 8). In October 1995, the need was also recognized
internationally by the workshop on efficacy and radiation safety in
interventional radiology, sponsored jointly by the World Health
Organization and the Institute of Radiation Hygiene, Radiation
Protection Ministry, Federal Republic of Germany (Ref. 23). Recently,
requirements for displays of irradiation parameters have been
incorporated into an international standard for x-ray systems for
interventional radiology (Ref. 24). With the advent of commercially
available and relatively inexpensive means to measure and display real-
time AKR and cumulative air kerma produced by fluoroscopic systems
(Ref. 25), it is feasible as well as desirable to require that this
information be directly observable by fluoroscopists at their working
positions.
The proposed display requirements would apply to all types of newly
manufactured fluoroscopic equipment (i.e., from systems found in
cardiac catheterization suites, to equipment used for upper
gastrointestinal fluoroscopy, to ``mini'' C-arms, and also to each
fluoroscopic x-ray tube as part of any system). FDA invites comments
about whether these requirements would be suitable to all types, or to
a limited set of fluoroscopic equipment, namely, to stationary C-arm
fluoroscopes that are typically used in interventional procedures.
1. Fluoroscopic Irradiation Time, Display, and Signal
Fluoroscopic irradiation time is profoundly tied to patient dose in
a complex way that involves many other factors (e.g., see Ref. 26). FDA
believes it advantageous to require that cumulative irradiation-time
values be treated in their own right, in addition to the other
variables cited in the proposed Sec. 1020.32(k), as radiological
parameters whose control would facilitate radiation-protection
optimization. Physician members of TEPRSSC pointed out at its September
1998 meeting that irradiation time is the single fundamental variable
over which a physician using fluoroscopy has the most direct and
easiest control through activating or deactivating x-ray production,
typically by means of a pedal switch (Ref. 27).
FDA proposes to add Sec. 1020.32(h)(2) to the regulations to
change the current fluoroscopic timer requirement in two ways. First,
Sec. 1020.32(h)(2)(i) would require that the values of the cumulative
irradiation times associated with each of the fluoroscopic tubes of a
system used in an examination or procedure be displayed to the
fluoroscopist at his or her working position. The displayed values
would be indicated from the beginning, throughout, and after an
examination ends, available until the cumulative irradiation timer is
reset to zero prior to a new examination. Second, Sec.
1020.32(h)(2)(ii) would require an audible signal cycle different from
that of current equipment for each x-ray tube used during an
examination or procedure. Contrary to the current provision that allows
the timing device to be preset to any interval up until a maximum
cumulative irradiation time of 5 minutes, FDA proposes that a signal
audible to the fluoroscopist sound at each fixed interval of 5 minutes
of irradiation time. Also contrary to the current requirement, instead
of sounding until reset, the audible signal would sound (while x-rays
are produced) for a minimum of only 1 second, after which the signal
could stop until a subsequent 5 minutes of irradiation elapses. The
audible signal would not affect the production of x-rays, the display
of cumulative irradiation-time values required by Sec.
1020.32(h)(2)(i), or any of the other displays proposed in Sec.
1020.32(k).
Considering advice offered at the 1998 TEPRSSC meeting (Ref. 27),
FDA now believes that a fixed, standard (5 minute) period for an alert
signal would avoid potential confusion that could ensue with a
fluoroscopic timer that is variably preset. For example, such confusion
could arise in a busy clinical facility with many different users,
where fluoroscopists might not be aware of the need to readjust alert
intervals that had been changed previously by other fluoroscopists to
accommodate the individual protocol requirements associated with
particular patient examinations. Furthermore, FDA believes that an
audible signal of short duration would be a more effective and useful
alert than a signal that sounds continuously, requires a reset, and
therefore, could pose a distraction to users. FDA seeks comments about
the audible signal cycle in proposed Sec. 1020.32(h)(2)(ii),
particularly in comparison to the suggested alternative below that is
not currently in the proposal.
As an alternative approach, the selection of the time period until
the alarm sounds could be at the discretion of the fluoroscopist. The
timer could be preset to any period (less than, equal to, or greater
than 5 minutes), or preset even to not sound at all. Under this
approach, before an examination or procedure, the fluoroscopist could
select a period beyond which an audible signal would sound until the
timer could be reset (or else sound briefly then remain silent until
the preset fluoroscopic period elapses again). Presuming clinicians
maintain personal cognizance of fluoroscopic timer options and
adaptability, such alternatives would offer them flexibility and
opportunity to apply standard features of equipment operation to their
[[Page 76066]]
own individual clinical protocols and practices.
FDA also seeks comment on whether the display of the cumulative
irradiation time should be visible to the fluoroscopist at his or her
working position or whether it is sufficient to display the cumulative
time at the control console. It has been suggested that this display
should be available to the fluoroscopist to permit constant monitoring
by the fluoroscopist. Other opinions are that such a display at the
working position would only add confusion to an already complex visual
environment, and display of the cumulative irradiation time at the x-
ray control would make the information available in any case. Display
at the fluoroscopist's working position may be slightly more complex or
costly than display at the x-ray control.
2. Displays of Air Kerma Rate and Cumulative Air Kerma
FDA believes that a requirement for displays of AKR and cumulative
air kerma values would significantly advance the optimization of
radiation safety, in consideration of recent developments in clinical
practice and technology (Refs. 23, 25, and 26), an evolving consensus
for a radiation-protection framework (Refs. 14 to 17), and specific
guidance (Refs. 18 to 20). Air kerma and AKR are fundamental
radiological quantities of the amount and rate of charged-particle
kinetic energy liberated per mass of air traversed by incident x-rays
(Ref. 1). For this reason, FDA proposes to add Sec. 1020.32(k) to
require that all new fluoroscopic systems be capable of displaying
real-time values of the AKR and cumulative air kerma delivered by each
x-ray tube at reference locations representative of x-ray beam entry to
the patient skin surface. These displays would be directly discernible
at the fluoroscopist's working position, and the displayed values would
deviate by no more than +/-25 percent from actual values. To elucidate
these requirements and those of the other proposed amendments, the
definitions of the terms ``fluoroscopy,'' ``mode of operation,'' ``and
radiography'' are proposed in Sec. 1020.30(b). The utility of the
display requirements could be broadly leveraged among practitioners in
a variety of clinical settings through familiarization with relatively
standardized display formats. Such standardization is proposed in Sec.
1020.32(k)(1) through (k)(7), where the particular requirements
proposed conform generally to those of the recently published IEC
standard (Ref. 24).
During fluoroscopy or while recording images during a fluoroscopic
procedure, the displayed value of the AKR would represent in real time
the magnitude of air kerma per unit time being delivered at any
geometrical point within a specified reference locus. The displayed
value of the cumulative air kerma would represent a sum of two parts:
(1) The fluoroscopic AKR integrated over an interval until update, and
(2) all contributions to the air kerma (at any point in the same
reference locus) from radiography occurring in that interval. The
cumulative air kerma would be updated throughout the examination or
procedure, and the integration interval would be the time between the
start of an examination or procedure and the end of the most recent
episode of either fluoroscopy or radiography during that same
examination or procedure.
For each x-ray tube used during fluoroscopy or during recording of
fluoroscopy, the value of the AKR will be displayed. After the
cessation of fluoroscopy, the cumulative air kerma will be displayed
and will remain displayed until the resumption of fluoroscopy or a
radiographic mode is activated or the display is reset for a new
patient or procedure. Thus, the cumulative air kerma will be displayed
after x-ray production ceases from either fluoroscopy or radiography.
Values of the AKR are displayed at times other than those for the
cumulative air kerma in order to underscore the distinction between
these two variables and also to reduce the potential for overwhelming
the fluoroscopist with too much information presented at once. At any
particular moment during an examination or procedure, only values of
the irradiation time and AKR (or cumulative air kerma) would be on
display for each tube used. If, for example, a biplane fluoroscopic
system were used in some cardiac catheterization procedure, two
separate sets of values--one set for each of the x-ray tubes of the
biplane--would be displayed. Under such circumstances of multiple
presentations of related information, it is important that the values
displayed be distinguishable enough from each other to be easily
recognized and associated with the different radiological variables
they represent. For this reason, FDA proposes in Sec. 1020.32(h)(2)(i)
and (k)(3) to require that the units of measurement be displayed as
well as the values per se. FDA also proposes in Sec. 1020.32(k)(1) and
(k)(2) to require that the measurement units mGy/min and mGy be
displayed respectively alongside the values for AKR and cumulative air
kerma. These values would serve as a labeling distinction to preclude
potential confusion of the quantities.
As measures of fundamental radiological quantities, the displayed
values of AKR and cumulative air kerma would refer to free-in-air
irradiation conditions (i.e., their evaluations would be made minus any
contributions of scatter radiation, particularly contributions
backscattered from a patient (or from a measurement phantom)). Also,
the displayed values would refer to irradiation conditions at a
reference location (i.e., at any geometrical point contained within a
specific reference locus defined according to the type of fluoroscopic
system). Each reference location is intended to represent, at least
nominally, a place of x-ray beam entry to the patient skin. For
fluoroscopes with the x-ray source below or above the table, or of the
lateral type, Sec. 1020.32(k)(5)(i) would have skin-entrance reference
locations correspond identically and respectively to those specified in
Sec. 1020.32(d)(3)(i), (d)(3)(ii), or (d)(3)(v). These locations
define the geometry for measuring compliance with the regulatory maxima
of the AKR.
For C-arm type fluoroscopes, however, in many cases the locations
proposed for measuring compliance with the regulatory maxima of the
AKR, given in Sec. 1020.32(d)(3)(iii) and (d)(3)(iv), would not
suitably represent where the x-ray field enters the patient skin. This
is especially true for oblique angulations and extended distances
between the x-ray source and image receptor. Therefore, in Sec.
1020.32(k)(5)(ii), for C-arm systems, FDA is proposing a skin-entrance
reference location for display quantities that is different from the
location for measuring compliance with regulatory AKR limits. For
evaluation of displayed values, the skin-entrance reference location
would be either 15 cm from the isocenter toward the x-ray source along
the beam axis (irrespective of angulation) or, alternatively, along the
beam axis at a point deemed by the manufacturer to represent the
intersection of the x-ray beam and the entrance surface of the patient
skin. A definition of ``isocenter'' is proposed in Sec. 1020.30(b).
Proposed Sec. 1020.32(k)(5)(ii) would allow manufacturers to choose
either the 15-cm locus or specify the alternative. The alternative
locus would offer manufacturers flexibility to provide systems that
could evaluate AKR and cumulative air kerma in closer proximity to
actual places of x-ray beam entry to patients than could systems with
reference skin entrance defined
[[Page 76067]]
generically at a 15-cm locus from the isocenter. An alternative skin-
entrance reference location may be particularly appropriate for mini C-
arm fluoroscopes (i.e., those with SID less than 45 cm, for which the
15-cm locus from the isocenter may be physically unrealizable). In any
case, new paragraphs Sec. 1020.30(h)(6)(iii) and (h)(6)(iv) would
require that manufacturers identify to the user the spatial coordinates
of the irradiation location to which displayed values refer and also
provide a rationale justifying any reference location identified as an
alternative to the 15-cm locus.
In patient examinations or procedures with C-arm systems, one
possible result of having reference locations of x-ray beam skin-entry
different from the measurement sites for AKR compliance is that
displayed values could actually exceed the regulatory maxima even
though the system is fully compliant. Such a situation could arise for
some irradiation geometry when the reference skin-entrance location is
closer to the x-ray source than is the site for measuring compliance.
Displayed values of the AKR and cumulative air kerma are intended to
inform the fluoroscopist of radiation burden to the patient.
Conversely, the AKR regulatory maxima, practicably measured 30 cm from
the imaging-assembly input, according to Sec. 1020.32(d)(3)(iii) or at
the minimum SSD according to Sec. 1020.32(d)(3)(iv), are intended to
impose upper limits on radiation output that are compatible with the
levels needed by the imaging chain for adequate fluoroscopic
visualization.
Reset of the displays to zero would occur between sessions with
successive patients. Before reset, a final value of the cumulative air
kerma may serve to reinforce an association between the culmination of
a radiological examination or procedure and the radiation burden
incurred by the patient. FDA believes that the availability of this
value would greatly facilitate the implementation of previously
published recommendations (Refs. 18 to 20) on recording information in
the patient's medical record to identify the potential for serious x-
ray-induced skin injuries in order to avoid them.
L. ``Last-Image Hold'' Feature on Fluoroscopic Systems (Proposed Sec.
1020.32(j))
FDA proposes to add a paragraph to require that all fluoroscopic x-
ray systems be provided with a means to continuously display the last
image acquired prior to termination of exposure.
The wide availability of electronic methods for the recording and
displaying of video images makes possible the provision of a ``last-
image hold'' or ``freeze-frame'' capability on fluoroscopic x-ray
systems. This feature allows the fluoroscopic x-ray system to
continuously present a static image of the last fluoroscopic scene
captured or presented at termination of the fluoroscopic exposure. This
feature also provides the user with the ability to conveniently view
fluoroscopic images without continuously irradiating the patient.
This feature is especially useful in procedures such as
fluoroscopically-guided needle placement for biopsy or drainage,
catheter or tube placement, and other diagnostic or therapeutic
interventional procedures. Systems provided with this feature reduce
fluoroscopic exposure times while enabling extended examination and
planning during fluoroscopically-guided procedures.
This capability is provided as a basic or optional feature on many
currently marketed fluoroscopic systems. Many individuals have
expressed the opinion that because of the radiation dose reduction
afforded by such a feature, it should be provided on all new
fluoroscopic systems. Such a recommendation was strongly endorsed at
the workshop on fluoroscopy in 1992 (Ref. 8). In addition, a
requirement for this capability is included in the recently published
IEC standard for the safety of x-ray equipment for interventional
radiology (Ref. 24). Establishing this requirement would assure that
all new fluoroscopic systems have this patient radiation dose reduction
feature and that it is available when its use is appropriate. Without
such a requirement, some systems may for economic reasons continue to
be purchased without this feature, thereby denying dose reduction
benefits to patients.
Proposed Sec. 1020.32(j) would permit the displayed image to be
obtained from the last or a combination of the last few fluoroscopic
video frames obtained just prior to termination of fluoroscopic
exposure or by an alternative implementation via a radiographic
exposure automatically produced at termination of the fluoroscopic
exposure. Comments are solicited as to whether these approaches to
implementation of last image-hold are appropriate and needed.
M. Modification of Previously Manufactured and Certified Equipment
FDA proposes to add language to Sec. 1020.32(d)(1)(iv) and (h) to
make explicit the opportunity under Sec. 1020.30(q) for modifications
to be made to existing certified x-ray systems. Modifications are
currently permitted as long as the modification does not result in a
failure to comply with the requirements of the performance standard.
Changes in performance resulting from amendments to the performance
standard often result in enhanced radiation safety or features not
available on previously manufactured and certified systems.
The existing performance standard requires manufacturers to certify
that their products meet the applicable performance requirements in
effect at the time of manufacture. Therefore, amendments to the
performance standard are generally not retroactive and effective dates
implementing the standard are specified in the regulations. Usually, a
1-year effective date is provided in order to allow manufacturers time
to adjust manufacturing and assembly of their products under the new or
amended regulations. Indeed, it would be unreasonable to require the
manufacturer to retrofit or to remanufacture previously produced
products because of a change in the standard for equipment that could
have a useful life of 20 or more years.
In particular, the performance requirements regarding maximum
exposure rate limits (proposed to become maximum AKR limits),
established in 1994 (59 FR 26402), and the proposed requirements in
Sec. 1020.32(h) for fluoroscopic timers are requirements or
performance features that users of older fluoroscopic equipment may
wish to implement on their systems. The earlier amendment in 1994 and
the current proposal apply to new equipment manufactured after the
effective date of the amendment. The language proposed for inclusion in
Sec. 1020.32(d) and (h) would provide a mechanism for users of older
equipment to obtain the performance required under the proposed
amendments. These changes would allow older systems to be modified to
meet the maximum AKR limit and fluoroscopic timer performance that will
be required under the proposed requirements.
The owner of the fluoroscopic system modified under Sec.
1020.30(q) is responsible for assuring that the modified x-ray system
complies with the applicable requirements of the performance standard
following the modification. The modification to the system may be
accomplished by a third party or by the original equipment
manufacturer. The system owner, however, is responsible for assuring,
[[Page 76068]]
through contract requirements with the party performing the
modification or through testing, that the modified system complies with
the standard following the modification.
N. Modification of Warning Label (Sec. 1020.30(j))
FDA proposes to modify the language of the warning label required
by Sec. 1020.30(j). The current statement warns that safe exposure
factors and operating instructions must be followed. FDA proposes to
modify the warning label statement by adding the phrase ``maintenance
schedules.'' This addition incorporates the suggestion of the TEPRSSC
and further emphasizes the need for diagnostic x-ray systems to be
properly maintained and calibrated. Manufacturers of diagnostic x-ray
systems are required under Sec. 1020.30(h)(1)(ii) to provide a
schedule of the maintenance necessary to keep the equipment in
compliance with the performance standard. The standard places no
requirement on owners or users of diagnostic systems to properly
maintain these systems. However, the revised wording of the warning
label is intended to alert users and facility administrators of the
need to properly maintain the systems.
O. Corrections of Sec. 1020.31(f)(3) and (m)
FDA proposes to correct oversights in Sec. 1020.31(f)(3) and (m)
that occurred when the July 2, 1999, amendment was published. Section
1020.31(f)(3) addresses the x-ray field limitation requirement for
mammographic x-ray systems and Sec. 1020.31(m) addresses the primary
barrier required for mammographic x-ray systems. Prior to September 30,
1999 (the effective date of the final rule), the heading to Sec.
1020.31(m) was ``Transmission limit for image receptor supporting
devices used for mammography.''
When an existing radiation safety performance standard is amended,
the new or modified requirement applies only to products that are
manufactured after the effective date of the amendment. Normally, the
requirement that existed prior to the amendment is retained in the Code
of Federal Regulations (CFR) to provide a record of the requirements of
the standard applicable to products on their date of manufacture. When
the final rule amending Sec. 1020.31(f)(3) and (m) was published on
July 2, 1999, the provisions describing the requirements for equipment
manufactured prior to September were inadvertently omitted. Thus, the
CFR (21 CFR part 1020) has no record of the requirements imposed by
Sec. 1020.31(f)(3) and (m) for equipment manufactured between the
initial effective dates for Sec. 1020.31(f)(3) and (m) and September
30, 1999. To correct this oversight, FDA proposes to reinstate the
provisions describing the requirements that apply to equipment
manufactured prior to September 30, 1999, under the earlier versions of
Sec. 1020.31(f)(3) and (m). This correction will provide a record of
the requirements applicable before September 30, 1999, and close the
gap that exists as a result of the oversight in the publication of the
final rule.
Additionally, further review of this issue revealed that the
original publication of Sec. 1020.31(f)(3) in 1977 (42 FR 44230) did
not indicate an effective date for this paragraph, which was November
1, 1977. FDA proposes to insert the omitted effective date. The
omission was of little consequence because the original requirement
reflected the then current designs of mammographic systems. FDA
proposes to insert the date to provide an accurate record of the
applicable x-ray field limitation requirements as a function of the
date of manufacture of mammographic x-ray systems.
No changes in the previously applicable or current requirements are
proposed or intended by these corrections to Sec. 1020.31(f)(3) and
(m). The corrections are only intended to make explicit the current or
previously applicable requirements that existed on the date of
manufacture.
FDA proposes to revise Sec. 1020.31(f) by adding Sec.
1020.31(f)(3)(i), the requirement applicable to equipment manufactured
on or after November 1, 1977, and before September 30, 1999. The
current requirement, applicable to equipment manufactured after
September 30, 1999, would be Sec. 1020.31(f)(3)(ii). Section
1020.31(f)(3)(iii) would contain the requirement for permanent markings
that are applicable to all equipment manufactured after November 1,
1977.
FDA proposes to amend Sec. 1020.31(m). Section 1020.31(m)(1) would
be revised to contain the requirement applicable to systems
manufactured on or after September 5, 1978, and before September 30,
1999; such requirement was previously omitted. Section 1020.31(m)(2)
would be revised to contain the current requirements applicable to
equipment manufactured after September 30, 1999, in Sec.
1020.31(m)(2)(i), (m)(2)(ii), (m)(2)(iii), and (m)(2)(iv). Section
1020.31(m)(3) would be revised to contain the description of the method
for measuring compliance; such description is common to both Sec.
1020.31(m)(1) and (m)(2). A minor technical clarification is also
proposed in Sec. 1020.31(m)(2)(ii) where the term ``x-ray tube'' found
in current Sec. 1020.31(m)(2) is replaced by the term ``x-ray system''
to reflect the fact that it is the x-ray system, not the x-ray tube,
that controls initiation of x-ray exposure. This change does not change
the intent or effect of the requirement.
P. Corrections to Reflect Changes in Organizational Name, Address, and
Law (Sec. 1020.30(c), (d), and (q))
FDA proposes to amend Sec. 1020.30(c) to reflect the current
organizational title of the Office of Compliance of the Center for
Devices and Radiological Health. FDA also proposes in Sec. 1020.30(d)
to remove the specific address that is subject to change from time to
time. Additionally, FDA proposes to amend paragraph Sec. 1020.30(q) to
reflect the transfer of sections 358(a)(5) and 360B(b) of the PHS Act
to the act by the SMDA.
Q. Removal of Reference to Special Attachments for Mammography
FDA proposes to remove reference to ``special attachments for
mammography'' in Sec. 1020.31(d) and (e). The Mammography Quality
Standards established in part 900 (21 CFR part 900), particularly Sec.
900.12(b)(1), require that only diagnostic x-ray systems designed
specifically for mammography be used to perform mammography in the
United States. Therefore, the use of special attachments intended for
use with general-purpose diagnostic x-ray systems to perform
mammography is inappropriate. No such devices may continue to be used,
and retaining this reference in the standard would imply that such
devices or components were acceptable.
R. Change to the Applicability Statement for Sec. 1020.32
FDA proposes in the applicability statement of Sec. 1020.32 to
remove the reference to ``fluoroscopy'' and replace it with
``fluoroscopic imaging'' and to remove ``recording of images through an
image intensifier tube'' and replace this reference with ``radiographic
imaging when the radiographic images are recorded from the fluoroscopic
image receptor.'' This change is necessary to clarify the applicability
of this section and to incorporate the proposed requirements addressing
the production of radiographic images for the last image hold feature.
S. Republication of Sec. Sec. 1020.30, 1020.31, and 1020.32
Because of the large number of proposed changes in Sec. Sec.
1020.30,
[[Page 76069]]
1020.31, and 1020.32, FDA is republishing these entire sections,
including the proposed amendments, rather than publishing only the
proposed individual changes to these sections. Although some of the
paragraphs in these sections are not changed by this proposal,
republication of the entire sections will result in a more reader-
friendly version when the final regulation is published.
III. Proposed Effective Date
FDA proposes that any final rule based on this proposal become
effective 1 year after the date of publication of the final rule in the
Federal Register.
IV. Environmental Impact
The agency has determined under 21 CFR 25.30(i) and 25.34(c) that
this action is of a type that does not individually or cumulatively
have a significant effect on the human environment. Therefore, neither
an environmental assessment nor an environmental impact statement is
required.
V. Paperwork Reduction Act of 1995
A. Summary
This proposed rule contains information collection provisions that
are subject to review by OMB under the Paperwork Reduction Act of 1995
(PRA) (44 U.S.C. 3501-3502). A description of these provisions is given
in the following paragraphs with an estimate of the annual reporting
and recordkeeping burden. Included in the estimate is the time for
reviewing instructions, searching existing data sources, gathering and
maintaining the data needed, and completing and reviewing each
collection of information.
The information collection burden of the current performance
standard is covered by an existing information collection clearance,
OMB control number 0190-0025. FDA is seeking new information collection
clearance for proposed Sec. Sec. 1020.30(h)(5) and (6), and
1020.32(j)(4).
FDA invites comments on: (1) Whether the proposed collection of
information is necessary for the proper performance of FDA's functions,
including whether the information will have practical utility; (2) the
accuracy of FDA's estimate of the burden of the proposed collection of
information, including the validity of the methodology and assumptions
used; (3) ways to enhance the quality, utility, and clarity of the
information to be collected; and (4) ways to minimize the burden of the
collection of information on respondents, including through the use of
automated collection techniques, when appropriate, and other forms of
information technology.
Performance Standard for Diagnostic X-Ray Systems and their Major
Components (21 CFR 1020.30 and 1020.32 amended)
Description: FDA is proposing to amend the performance standard for
diagnostic x-ray systems by establishing, among other things,
requirements for several new equipment features on all new fluoroscopic
x-ray systems. In the current performance standard, Sec. 1020.30(h)
requires that manufacturers provide to purchasers of x-ray equipment,
and to others upon request, manuals or instruction sheets that contain
technical and safety information. This required information is
necessary for all purchasers (users of the equipment) to have in order
to safely operate the equipment. Section 1020.30(h) currently describes
the information that must be provided.
The proposed rule would add to Sec. 1020.30(h) paragraphs (5) and
(6) describing additional information that would need to be included in
these manuals or instructions. In addition, proposed Sec.
1020.32(j)(4) would specify additional descriptive information to be
included in the user manuals for fluoroscopic x-ray systems required by
Sec. 1020.30(h). This additional information would be descriptions of
features of the x-ray equipment required by the proposed amendments and
information determined to be appropriate and necessary for safe
operation of the equipment.
Description of Respondents: Manufacturers of fluoroscopic x-ray
systems that introduce fluoroscopic x-ray systems into commerce
following the effective date of the proposed amendments. FDA estimates
the burden of this collection of information as follows:
Table 4.--Estimated Average Annual Reporting Burden for the First
Year\1\
------------------------------------------------------------------------
Annual
No. of Frequency Total Hours Total
21 CFR Section Respondents per Annual per Hours
Respondent Responses Response
------------------------------------------------------------------------
1020.30(h)(5) and 20 10 200 180 36,000
(h)(6) and
1020.32(j)(4)
------------------------------------------------------------------------
\1\ There are no capital costs or operating and maintenance costs
associated with this collection of information.
Table 5.--Estimated Average Annual Reporting Burden for Second and
Following Year\1\
------------------------------------------------------------------------
Annual
No. of Frequency Total Hours Total
21 CFR Section Respondents per Annual per Hours
Respondent Responses Response
------------------------------------------------------------------------
1020.30(h)(5) and 20 5 100 180 18,000
(h)(6) and
1020.32(j)(4)
------------------------------------------------------------------------
\1\ There are no capital costs or operating and maintenance costs
associated with this collection of information.
B. Estimate of Burden
As described in the assessment of the cost impact of the proposed
amendment (Ref. 33), it is estimated that there are about 20
manufacturers of fluoroscopic x-ray systems who market in the United
States. Each of these manufacturers is estimated to market about 10
distinct models of fluoroscopic x-ray systems. Immediately following
the effective date of the proposed amendments, for each model of
fluoroscopic x-ray system that manufacturers continue to market, each
manufacturer would have to supplement the user instructions to include
the additional information required by the proposed amendments.
Manufacturers already develop, produce, and provide x-ray system
user manuals or instructions containing the information necessary to
operate the systems, as well as the specific information required to be
provided by the existing standard in current Sec. 1020.30(h).
Therefore, it is assumed that no significant additional capital,
[[Page 76070]]
operating, or maintenance costs will occur to the manufacturers in
connection with the provision of the newly required information. The
manufacturers already have procedures and methods for developing and
producing the user's manuals, and the additional information required
by the proposed requirements is expected to only add a few printed
pages to these already extensive manuals or documents.
The burden that will occur to manufacturers from the new
requirements for information in the user's manuals will be the effort
required to develop, draft, review, and approve the new information.
The information or data to be contained within the new user
instructions will already be available to the manufacturers from their
design, testing, validation, or other product-development documents.
The burden will consist of gathering the relevant information from
these documents and preparing the additional instructions from this
information.
It is estimated that about 3 weeks of professional staff time (120
hours) would be required to gather the required information for a
single model of an x-ray system. It is estimated that an additional 6
weeks (240 hours) of professional staff time would be required to
draft, edit, design, layout, review, and approve the new portions of
the user's manual or information required by the proposed amendments.
Hence FDA estimates a total of 360 hours to prepare the new user
information that would be required for each model.
For a given manufacturer, FDA anticipates that every distinct model
of fluoroscopic system will not require a separate development of this
additional information. Because it is thought highly likely that
several models of fluoroscopic x-ray systems from a given manufacturer
will share common design aspects, it is anticipated that similar means
for meeting the proposed requirement for display of exposure time, air
kerma rate, and cumulative air kerma and the requirement for the last-
image-hold feature will exist on multiple models of a single
manufacturer's products. Such common design aspects for multiple models
will reduce the burden on manufacturers to develop new user
information. Hence the average time required to prepare new user
information for all of a manufacturer's models will be correspondingly
reduced. It is assumed that the applicability of the new user
information developed to multiple models will reduce the average burden
from the 360 hours to about 180 hours per model under the assumption
that each set of user information for a given equipment feature design
will be a applicable to at least two different models of a
manufacturer's fluoroscopic systems. Under this assumption, the total
estimated time for preparing the new user information that would be
required is 36,000 hours, as shown in table 4 of this document.
In each succeeding year the burden will be less, as the reporting
requirement will apply only to the new models developed and introduced
by the manufacturers in that specific year. FDA assumes that every two
years each manufacturer will replace each of its models with a newer
model requiring new user information. The multiple system applicability
of this information is accounted for by also assuming that each new
model only requires 180 hours of effort to develop the required
information. These assumptions result in an estimated burden of 18,000
hours for each of the years following the initial year of applicability
of the proposed amendments, as shown in table 5 of this document.
In compliance with the PRA (44 U.S.C. 3507(d)), the agency has
submitted the information collection provisions of this proposed rule
to OMB for review. Interested persons are requested to send comments
regarding information collection to the Office of Information and
Regulatory Affairs, OMB (see ADDRESSES).
VI. Analysis of Impacts
A. Introduction
FDA has examined the impacts of this proposed rule under Executive
Order 12866, the Regulatory Flexibility Act (5 U.S.C. 601-612), and the
Unfunded Mandates Reform Act of 1995 (Public Law 104-4) (UMRA).
Executive Order 12866 directs agencies to assess all costs and benefits
of available regulatory alternatives and, when regulation is necessary,
to select regulatory approaches that maximize net benefits (including
potential economic, environmental, public health and safety, and other
advantages; distributive impacts; and equity). The agency believes that
this proposed rule is consistent with the regulatory philosophy and
principles identified in the Executive order. In addition the proposed
rule is economically significant under Executive Order 12866 and is
major under the Congressional Review Act. Therefore the proposal is
subject to review under the Executive order.
The Regulatory Flexibility Act requires agencies to analyze
regulatory options that would minimize any significant impact on small
entities. An analysis of available information suggests that costs to
small entities are likely to be significant, as described in the
following analysis. FDA believes that this proposed regulation will
likely have a significant impact on a substantial number of small
entities, and it conducted an initial regulatory flexibility analysis
(IRFA) to ensure that any such impacts were assessed and to alert any
potentially impacted entities of the opportunity to submit comments.
Section 202(a) of the UMRA requires that agencies prepare a written
statement of anticipated costs and benefits before proposing any rule
that may result in an expenditure by State, local, and tribal
governments, in the aggregate, or by the private sector, of $100
million in any one year (adjusted annually for inflation). The UMRA
does not require FDA to prepare a statement of costs and benefits for
the proposed rule because the proposed rule is not expected to result
in any 1-year expenditure that would exceed $100 million adjusted for
inflation. The current inflation-adjusted statutory threshold is about
$110 million.
The agency has conducted preliminary analyses of the proposed rule,
including a consideration of alternatives, and has determined that the
proposed rule is consistent with the principles set forth in the
Executive order and in these statutes. The costs and benefits of the
proposed rule have been assessed in two separate preliminary analyses
that are described in section VI of this document and that are
available at the Dockets Management Branch (see ADDRESSES) for review.
As reviewed below, these preliminary analyses have an estimated upper
limit to the annual cost of $30.8 million during the first 10 years
after the effective date of the proposed amendments. The analysis of
benefits projects an average annual amortized pecuniary savings in the
first 10 years after the effective date of at least $320 million, with
an estimated 90 percent confidence interval spanning a range between
$88.35 million and $1.160 billion. FDA believes this analysis of
impacts complies with Executive Order 12866, and that the proposed rule
is a significant regulatory action as defined by the Executive order.
Because of the preliminary nature of these cost and benefit analyses
and estimates, FDA requests comments on any aspect of their
methodologies, assumptions, and projections. Comments may be
[[Page 76071]]
submitted to the Dockets Management Branch (see ADDRESSES).
B. Objective of the Proposed Rule
The primary objective of the proposed rule is to improve the public
health by reducing exposure to and detriment associated with
unnecessary ionizing radiation from diagnostic x-ray systems, while
maintaining the diagnostic quality of the images. The proposed rule
would meet this objective by requiring features on newly manufactured
x-ray systems that physicians may use to minimize unnecessary or
unnecessarily large doses of radiation that could result in adverse
health effects to patients and health care personnel. Such adverse
effects from x-ray exposure can include acute skin injury and an
increased potential for cancer or genetic damage. The secondary
objectives of this proposed rule are to bring the performance standard
up to date with recent and emerging technological advances in the
design of fluoroscopic x-ray systems and to assure appropriate
radiation safety for these designs. The proposed amendments would also
align the performance standard with performance requirements in current
international standards that were developed since the original
publication of the performance standard in 1972. In several instances,
the international standards contain more stringent requirements on
aspects of system performance than the current U.S. performance
standard. The proposed changes would ensure that the different safety
standards are harmonized to the extent that systems meeting one
standard will not be in conflict with the other. Such harmonization of
standards lessens the regulatory burdens on manufacturers desiring to
market systems in the global market.
The proposed amendments would require particular x-ray equipment
features reducing unnecessary radiation exposure and thereby yielding
net benefits. The amendments are necessary because the market will not
ensure that these equipment features will be adopted without a
government mandate for such features. Purchasers in health care
organizations have no incentive to demand the more expensive x-ray
equipment that would be required by these new amendments because they
perceive no institutional economic advantage in doing so as benefits
accrue mainly to patients. Furthermore, purchasers are more responsive
to physician attention to an immediate need for diagnostic and
interventional efficacy from the equipment than to a prospective
capability to reduce radiation-associated risk to patients many years
in the future. Patients, also focused on their immediate medical needs,
will not demand this equipment because they lack information and
knowledge about long-term radiation risk and about the highly technical
nature of x-ray equipment. Hence these proposed amendments are
necessary to realize the net benefits described in the following
analysis.
C. Risk Assessment
The risks to health that will be addressed by these amendments are
the adverse effects of exposure to ionizing radiation that can result
from procedures utilizing diagnostic x-ray equipment. These adverse
effects are well known and have been extensively studied and
documented. They are generally categorized into two types--
``deterministic'' and ``stochastic.'' Deterministic effects are those
that occur with certainty in days or weeks or months following
irradiation whose cumulative dose exceeds a threshold characteristic of
the effect. Above the threshold, the severity of the resulting injury
increases as the radiation dose increases. Examples of such effects are
the development of cataracts in the lens of the eye and skin ``burns.''
Skin is the tissue that often receives the highest dose from external
radiation sources such as diagnostic or therapeutic x-ray exposure.
Depending on the magnitude of the dose, skin injuries from radiation
can range in severity from reddening of the skin and hair loss to more
serious burn-like effects including localized tissue death that may
require skin grafts for treatment or may result in permanent
impairment. Stochastic effects are those that do not occur with
certainty, but if they appear, they generally appear as leukemia or
cancer one or several decades after the radiation exposure. The
probability of the effect occurring is proportional to the magnitude of
the radiation dose in the tissue.
The primary risk associated with radiation is the possibility of
patients developing cancer years after exposure, and the magnitude of
this cancer risk is generally regarded to increase with increasing
radiation dose. Consistent with the conservative approach to risk
assessment described by the National Council on Radiation Protection
and Measurements (Ref. 32), we assume a linear relationship between
cancer risk and dose. The slope of this relationship depends on age at
exposure and on gender. Our benefits analysis presented in section VI.H
is based on linear interpolations of cancer-mortality risk per dose
derived from BEIR V table 4-3 (Ref. 22) values reduced by a dose-rate
effectiveness factor of 2 for solid cancers (Ref. 30). The values used
in our analysis are represented in the following graph in figure 1 of
the excess lifetime-probability for death per dose associated with
radiation exposure.
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FDA underscores the overarching uncertainty in these projections
with the following statement adopted from CIRRPC Science Panel Report
No. 9 (Ref. 30):
The estimations of radiation-associated cancer deaths were
derived from linear extrapolation of nominal risk estimates for
lifetime total cancer mortality from doses of 0.1 Sv. Other methods
of extrapolation to the low-dose region could yield higher or lower
numerical estimates of cancer deaths. At this time studies of human
populations exposed at low doses are inadequate to demonstrate the
actual level of risk. There is scientific uncertainty about cancer
risk in the low-dose region below the range of epidemiologic
observation, and the possibility of no risk cannot be excluded.
We project that the equipment features that would be required by
three of the proposed amendments will promote the bulk of radiation
dose reduction and hence cancer risk reduction: (1) Displays of
radiation time, rate, and dose values; (2) more filtration of lower-
energy x rays; and (3) improved geometrical efficiency of the x-ray
field achieved through tighter collimation. We assume that the display
amendment would reduce dose on the order of 16 percent. This assumed
value is one-half of a 32 percent dose reduction observed for several
x-ray modalities in the United Kingdom (UK) between 1985 and 1995. We
assume that one-half of the UK dose reduction was due to technology
improvements alone, whereas the other half stemmed from the quality
assurance use of reference dose levels and patient dose evaluation. The
16 percent dose reduction that we project for the display amendment
thus presumes facility implementation of a quality assurance program
making use of the displayed values. This analysis and other
assumptions--6 percent dose reduction for the filtration amendment, 1
to 3 percent dose reduction for the collimation amendment--are detailed
in Ref. 29. We invite comment on these assumptions.
Until recently, the principle radiation detriment for patients
undergoing x-ray procedures was the risk of inducing cancer and, to a
lesser extent, heritable genetic malformations. Since 1992, however,
approximately 80 reports of serious radiation-induced skin injury
associated with fluoroscopically-guided interventional therapeutic
procedures have been published in the medical literature or reported to
FDA. Many of these injuries involved significant morbidity for the
affected patients. FDA's experience with reports of such adverse events
leads the agency to believe that the number of these injuries is very
likely underreported, given the total number of interventional
procedures currently performed. Additionally, there is the lack of any
clearly understood requirement or incentive for health care facilities
to report such injuries. With the advance of fluoroscopic technology
and the proliferating use of interventional procedures by practitioners
not traditionally specializing in the field, and therefore not
completely familiar with dose-sparing techniques, FDA expects an
increasing risk of radiation burns that warrants the changes to the x-
ray equipment performance standard through the proposed amendments.
D. Constraints on the Impact Analysis
It is FDA's opinion that the proposed amendments would offer public
health benefits that warrant their costs. However, the agency has had
difficulty thus far accessing pertinent information from stakeholders
to help quantify the impact of the proposal and alternatives. In view
of the limited information available with which to develop estimates of
the costs and benefits, FDA solicits comments, data, and opinions as to
whether the potential health benefits of the proposed amendments would
justify their costs. FDA will use all information and comments received
to revise the impact assessment in reaching a final determination as to
the appropriateness of the proposed amendments.
The principal costs associated with the proposed amendments would
be the increased costs to manufacturers to produce equipment that will
have the features required by the amendments. FDA has made an estimate
of potential cost. The cost estimate is based on a number of
assumptions designed to assure that the potential cost is not
underestimated. FDA anticipates that the actual costs of these
amendments to be significantly less than the upper-limit estimate
developed. Manufacturers of diagnostic x-ray systems are urged to
provide detailed comments on the anticipated costs of these amendments
that will enable refinement of these cost estimates.
The benefits that are expected to result from these amendments are
reductions in acute skin injuries and radiation-induced cancers. The
proposed amendments would have two types of impact that reduce patient
dose and associated radiation detriment without compromising image
quality.
The first type of change involves several newly required equipment
features that would directly affect the intensity or size of the x-ray
field. These are the requirements addressing x-ray beam quality, x-ray
field limitation, limits on maximum radiation exposure rate, and MSSD
for mini C-arm fluoroscopic systems. Almost all of the changes that
directly affect x-ray field size or intensity would bring the
performance standard requirements into agreement with existing
international voluntary standards. To the extent that these
requirements are included in voluntary standards that have a growing
influence in the international marketplace, the radiological community
has already recognized their benefit and appropriateness. Moreover,
harmonization within a single international framework would obviate the
expense for manufacturers to produce more than one line of products for
a single global marketplace.
The second type of change that would be required by these
amendments involves the information to be provided by the manufacturer
or directly by the system itself that may be utilized by the operator
to more efficiently use the x-ray system and thereby reduce patient
dose. There is wide support for and anticipation of these new features
by many knowledgeable users of fluoroscopic systems. Similar
requirements were recently included in a new international voluntary
standard.
E. Baseline Conditions
The cost of the proposed amendments to the x-ray equipment
performance standard would be borne primarily by manufacturers of
fluoroscopic systems. The cost for one of the nine proposed amendments
would also affect manufacturers of radiographic equipment and is
discussed in detail in Ref. 28. Therefore, this discussion will focus
primarily on fluoroscopy (i.e., the process of obtaining dynamic, real-
time images of patient anatomy).
X-ray imaging is used in medicine to obtain diagnostic information
on patient anatomy and disease processes or to visualize the delivery
of therapeutic interventions. X-ray imaging almost always involves a
tradeoff between the quality of the images needed to do the imaging
task and the magnitude of the radiation exposure required to produce
the image. Difficult imaging tasks may require increased radiation
exposure to produce the images unless some significant technological
change provides the needed image quality. Therefore, it is important
that users of x-ray systems have information regarding the radiation
exposures required for the images that are being produced in order to
make the appropriate risk-benefit decisions.
Equipment meeting the new standards in the proposed amendments
would provide image quality and diagnostic information identical to
equipment
[[Page 76074]]
meeting current standards. Therefore, the clinical usefulness of the
images provided would not change. The amendments would not affect the
delivery of x-ray imaging services because the reasons for performing
procedures, the number of patients having procedures, and the manner in
which procedures are scheduled and conducted would not be changed as a
result of the amendments. In addition, nothing in these amendments
would adversely affect the clinical information or results obtained
from these procedures. These amendments would result in x-ray systems
having features that automatically provide for more efficient use of
radiation or features that provide the physicians using the equipment
with immediate information related to patient dose, thus enabling more
informed and efficient use of radiation. These amendments would provide
physicians using fluoroscopic equipment with the means to actively
monitor patient radiation doses and minimize unnecessary exposure or
avoid doses that could result in radiation injury.
Estimates of the annual numbers of certain fluoroscopic procedures
performed in the United States during the years 1996 or 1997 were
developed, as described in Ref. 29, using data from several sources.
These estimates of the annual numbers of specific procedures were used
in the estimates of benefit from the proposed amendments. No attempt
was made to account for changes in the annual numbers of procedures in
future years, due to the large uncertainties in making such
projections. FDA also estimates that over 3 million fluoroscopically
guided interventional procedures are performed each year in the United
States. These procedures are described as ``interventional procedures''
because they accomplish some form of therapy for patients, often as an
alternative to more invasive and risky surgical procedures.
Interventional procedures may result in patient radiation doses in some
patients that approach or exceed the threshold doses known to cause
adverse health effects. The high doses occur because physicians utilize
the fluoroscopic images throughout the entire procedure, and such
procedures often require exposure times significantly longer than
conventional diagnostic procedures to guide the therapy.
FDA records indicate that about 12,000 medical diagnostic x-ray
systems are installed in the United States each year. Of these, 4,200
are fluoroscopic system installations. The proposed amendments would
apply only to those new systems manufactured after the effective date,
therefore affecting the 4,200 new fluoroscopic systems installed
annually and a small fraction of radiographic systems that do not
currently meet the proposed standard for x-ray beam quality.
In modeling the x-ray equipment market in the United States for the
purpose of developing estimates of the cost of these amendments, FDA
estimates that there are approximately a total of 40 manufacturers of
diagnostic x-ray systems in the United States and half of these (20)
market fluoroscopic systems and radiographic systems. It is assumed
that manufacturers of radiographic systems typically market 20 models
of radiographic systems, while manufacturers of fluoroscopic systems
market 10 different models of fluoroscopic systems.
F. The Proposed Amendments
As described in section II of this document, the proposed
regulations may be considered as nine significant amendments to the
current performance standard for diagnostic x-ray systems and other
minor supporting changes to the standard. The nine principal amendments
may be grouped into three major impact areas: (1) Amendments requiring
changes to equipment design and performance that would facilitate more
efficient use of radiation and provide means for reducing patient
exposure, (2) amendments improving the use of fluoroscopic systems
through enhanced information to users, and (3) amendments facilitating
the application of the standard to new features and technologies
associated with fluoroscopic systems.
Amendments requiring equipment changes include changes in x-ray
beam quality; provision of a means to add additional filtration;
changes in the x-ray field limitation requirements; provision of
displays of values of irradiation time, AKR, and cumulative air kerma;
the display of the last fluoroscopic image acquired (LIH feature);
specification of the MSSD for mini C-arm systems; and changes to the
requirement concerning maximum limits on entrance AKR. Amendments that
would result in improved information for users are those requiring
additional information to be provided in user instruction manuals.
Amendments facilitating the application of the standard to new
technologies include the recognition of SSXI devices, revisions of the
applicability sections, and establishment of additional definitions.
G. Benefits of the Proposed Amendments
The proposed amendments would benefit patients by enabling
physicians to reduce fluoroscopic radiation doses and associated
detriment and, hence, to use the radiation more efficiently to achieve
medical objectives. The health benefits of lowering doses are
reductions in the potential for radiation-induced cancers and in the
numbers of skin burns associated with higher levels of x-ray exposure
during fluoroscopically-guided therapeutic procedures. FDA believes
that the proposed amendments would not degrade the quality of
fluoroscopic images produced while reducing the radiation doses.
There is widespread agreement in the radiological community that
radiation doses to patients and staff should be kept ``as low as
reasonably achievable'' (ALARA) as a general principle of radiation
protection. In particular, moreover, recent experience has demonstrated
that in some few cases of fluoroscopically-guided interventional
procedures with especially long irradiation times, the magnitudes of
the radiation doses are large enough to cause serious injury to the
skin. A growing number of patients that are potentially at risk for
acute and long-term radiation injury makes it important to provide
fluoroscopic systems with features that will assist in reducing the
radiation to patients while continuing to accomplish the medical
objectives of the needed procedures.
The proposed amendments would require that fluoroscopic x-ray
systems provide equipment features that directly enable the user to
reduce radiation doses and maintain them ALARA. Furthermore, the
amendments would require provision of information to the user of the
equipment in the form of additional information in the user's manual or
instructions to enable improved use in a manner that minimizes patient
exposures and, by extension, occupational exposures to medical staff.
There is wide agreement that radiation exposures during fluoroscopy
are not optimized. For example, data from the 1991 Nationwide
Evaluation of X-ray Trends (NEXT) surveys of fluoroscopic x-ray systems
used for upper gastrointestinal tract examinations (upper GI exam)
indicate that the mean entrance AKR is typically 5 cGy/min for an adult
patient (Ref. 28). Properly maintained and adjusted fluoroscopic
systems are expected to be able to perform the imaging tasks associated
with the upper GI exam with
[[Page 76075]]
an entrance AKR of 2 cGy/min or less (Ref. 8). The NEXT survey data
indicate significant room for improvement in this aspect of
fluoroscopic system performance. The total patient dose could be
significantly reduced were the entrance AKR lowered to what is
currently reasonably achievable, and the features required by the
proposed amendments would facilitate this reduction.
The proposed features of LIH and real-time display of entrance AKR
and cumulative entrance air kerma values are intended to provide
fluoroscopists with means to better limit the patient radiation
exposure. The LIH feature would permit decision-making regarding the
procedure underway while visualizing the anatomy without continuing to
expose the patient. The air kerma- and AKR-value displays would provide
real-time feedback to the fluoroscopists and are anticipated to result
in improved fluoroscopist performance to limit radiation dose based on
the immediate availability of information regarding that dose.
Realization of the potential dose-reduction benefits would require
fluoroscopists to take advantage of these proposed features and
optimize the way they use fluoroscopic systems.
The potential impact of the change in the beam quality requirement,
which would apply to most radiographic and all fluoroscopic systems,
can be seen from the data on beam quality obtained from the FDA
Compliance Testing Program for the current standard. Since January 1,
1996, FDA has conducted 4,832 tests of beam quality, that is,
measurement of the HVL of the beam for newly installed x-ray systems.
Of these tests, only 15 systems did not meet the current HVL or beam
quality requirement. If the requirements for HVL contained in these
proposed amendments were used as the criteria for compliance, only 698
systems or 14.4 percent of the systems tested would have been found not
to have complied. This result suggests that at a minimum approximately
15 percent of recently installed medical x-ray systems would have their
beam quality improved and patient exposures reduced were the new
requirement in place and applicable to them.
Numerous examples are available in the literature that illustrate
the potential reduction in patient dose, while preserving image
quality, that can result from increased x-ray beam filtration.
Reference 7 demonstrates that the addition of 1.5 to 2.0 mm of aluminum
(Al) as additional filtration, which is the change required to enable
systems that just meet the current requirement to meet the proposed HVL
requirement, would result in about a 30 percent reduction in entrance
air kerma and about a 15 percent reduction in the integral dose for the
fluoroscopic examination modeled in the paper at 80 kVp tube potential.
Reduction in entrance skin dose (entrance air kerma) is relevant to
reducing the risk of deterministic injuries to the skin, while a
reduction in the integral dose is directly related to a reduction in
the risk of stochastic effects such as cancer induction. Other authors
have described dose reductions of a similar magnitude from increasing
filtration for radiographic systems.
The requirements proposed in these amendments implement many of the
suggestions and recommendations developed by members of the
radiological community at the 1992 Workshop on Fluoroscopy sponsored by
the American College of Radiology and FDA (Ref. 8). The recommendations
from this workshop stressed the need to provide users of fluoroscopy
with improved features enabling more informed use of this increasingly
complex equipment. In addition, three radiological professional
organizations indicated their opinions to FDA that radiologists would
use the new features to better manage patient radiation exposure.
H. Estimation of Benefits
Projected benefits are quantified below in terms of: (1) Collective
dose savings, (2) numbers of lives spared premature death associated
with radiation-induced cancer, (3) collective years of life spared
premature death, (4) numbers of reports of fluoroscopic skin burns
precluded, and (5) pecuniary estimates associated with the preceding
four items. The estimates represent average annual benefits projected
to ramp up during a 10-year interval in which new fluoroscopic systems
conforming to the proposed rules are phased into use in the United
States. (FDA assumes that 10 years after the effective date of the
proposed rules all fluoroscopic systems then in use would conform to
those rules and that associated recurring benefits would continue to
accrue at constant rates.) Annual pecuniary estimates that are averaged
over the 10-year ramp-up interval and that are associated with
prevention of cancer incidence, preclusion of premature mortality, and
obviation of cancer treatment are based on the projected numbers of
lives spared premature death. These pecuniary estimates are valued in
current dollars using a 7 percent discount rate covering the identical
10-year evaluation period used in the cost analysis (see section VI.I).
Based on an economic model of society's willingness to pay a premium
for high-risk jobs, we associate a value of $5 million for each
statistical death avoided, $25,000 for preclusion of each cancer
treatment, and $5,000 for preclusion of cancer's psychological impact.
Life benefits would be realized 20 years following exposure (after a
period of 10 years of cancer latency followed by a period of 10 years
of survival). Details, notes, and references for this analysis are
provided in Ref. 29. The low, middle, and high estimates in table 6 of
this document correspond respectively to the 5th, median, and 95th
percentile points of nominal probability distributions. Estimation of
the confidence intervals associated with these distributions is
explained in the following paragraphs.
Table 6.--Projections of Annual Benefits in United States
for display, collimation, and filtration rules applied to PTCA, CA, and UGI procedures\1\
----------------------------------------------------------------------------------------------------------------
5th Percentile Median 95th Percentile
----------------------------------------------------------------------------------------------------------------
Average Annual Dose and Life Savings in the First 10 Years ................ ................ ................
After Effective Date of Proposed Rules
----------------------------------------------------------------------------------------------------------------
Collective dose savings (person-sievert) 3,202 7,231 16,330
----------------------------------------------------------------------------------------------------------------
Number of lives spared premature death from cancer 62 223 808
----------------------------------------------------------------------------------------------------------------
Years of life spared premature death from cancer 1,131 4,094 14,818
----------------------------------------------------------------------------------------------------------------
[[Page 76076]]
Number of reported skin burns precluded 0.5 1.1 2.4
----------------------------------------------------------------------------------------------------------------
Average Annual Amortized Pecuniary Savings in the First 10 ................ ................ ................
Years After Effective Date of Proposed Rules
----------------------------------------------------------------------------------------------------------------
Prevention of premature death from cancer ($ millions) 78.61 285.03 1,032.75
----------------------------------------------------------------------------------------------------------------
Obviation of cancer treatment ($ millions) 9.71 35.21 127.56
----------------------------------------------------------------------------------------------------------------
Obviation of radiation burn treatment and loss ($ 0.03 0.07 0.16
millions)
----------------------------------------------------------------------------------------------------------------
Total ($ millions) 88.35 320.31 1,160.48
----------------------------------------------------------------------------------------------------------------
\1\ PTCA: percutaneous transluminal coronary angioplasty; CA: cardiac catheterization with coronary
arterlography or angiography; UGI: upper gastrointestinal fluoroscopy
For the most part, these projections are based on a benefits
analysis (Ref. 29, available at http://www.fda.gov/cdrh/radhlth/021501_xray.html
) whose domain is intended to be representative but
not exhaustive of prospective savings. To keep the analysis finite and
manageable, it is limited to the three proposed amendments (sections
II.E, II.F, and II.K of this document) that would most reduce radiation
dose in several of the most common fluoroscopic procedures. The
procedures considered are those of PTCA, CA, and UGI. There are other
very highly utilized fluoroscopic procedures, for example, the barium
enema examination, whose dose savings might be of comparable magnitude
to those of UGI, that are not included at all in this analysis. The
three amendments considered would require new fluoroscopic x-ray
systems to: (1) Display the rate, time and cumulative total of
radiation emission; (2) collimate the x-ray beam more efficiently; and
(3) filter out more of the low energy x-ray photons from the x-ray
beam. Proposed requirements for the source-skin distance for small c-
arm fluoroscopes (section II.J of this document) and for provision of
the last-image hold feature on all fluoroscopic systems (section II.L
of this document) will also directly reduce dose, but their dose
reductions are expected to be much smaller than those associated with
the preceding proposed changes. The remaining amendments can be
characterized as clarifications of the applicability of the standard,
changes in definitions, corrections of errors, and other changes that
contribute generally to the effectiveness of implementation of the
standard.
Most of the assumptions, rationales, and data sources underlying
the benefit projections are explicitly detailed in Ref. 29 and its
notes and references. That analysis, however, is incomplete insofar as
it refers only to a single set of point estimates. In order to develop
a range of projections with a nominally high level of confidence,
several additional assumptions are needed. Among the most important of
the underpinnings of the analysis are: (1) The projected percentage
dose reductions corresponding to the three amendments considered and
(2) the dependence on the risk estimates for cancer mortality from the
U.S. National Research Council Committee on the Biological Effects of
Ionizing Radiation (BEIR V) (Ref. 22). For the former, FDA assumes a
relative uncertainty of a factor of 2 (lower or higher) to represent
the range in projected dose reductions consistent with a range of
confidence of about 90 percent in the findings and assumptions (Ref.
29).
With respect to the dependence on the BEIR V estimates, FDA follows
two recommendations of the Office of Science and Technology Policy
(OSTP) Committee on Interagency Radiation Research and Policy
Coordination (CIRRPC) Science Panel Report No. 9 (Ref. 30) that
represent the Federal consensus position for radiation risk-benefit
evaluation: First, we apply a value of 2 as the dose-rate effectiveness
factor (DREF) in the projections of numbers of solid, non-leukemia
cancers. Adopting a DREF value of 2 in the analysis nearly halves the
Ref. 29 modal point projections of the numbers of lives and years of
life spared premature death from cancer. A DREF value of 2 implies that
diagnostic or interventional fluoroscopy is a relatively low dose-rate
modality. There are ambiguous assessments of that proposition: Although
BEIR V (Ref. 22, pp. 171, 220) considers most medical x-ray exposures
to correspond to high-dose rates (for which the DREF is assumed to
equal 1 for solid cancers), ICRP Publication 73 (Ref. 16, p. 6) states
just as unequivocally that risk factors reduced by a DREF larger than 1
(i.e., for low dose-rate modalities) ``are appropriate for all
diagnostic doses and to most of the doses in tissues remote from the
target tissues in radiotherapy.'' Recognizing these contrary views of
the detrimental biological effectiveness associated with the rates of
delivery of fluoroscopic radiation, we assume a factor of 2 uncertainty
in the DREF to span a 90 percent range of confidence. The second
recommendation that FDA adopts from CIRPPC Panel Report No. 9 (Ref. 30)
is the interpretation that a factor of 2 relative uncertainty
represents the BEIR V Committee's estimation of the 90 percent
confidence interval for mortality risk estimates (Ref. 22). The latter
value also agrees with that in the recent review of the United Nations
Scientific Committee on the Effects of Atomic Radiation in the
``UNSCEAR 2000 Report'' (Ref. 31).
All of the contributions of relative uncertainty appropriate for
the projections of collective dose savings, lives and years of life
spared premature death associated with radiation-induced cancer,
numbers of reports of fluoroscopic skin burns precluded, and associated
pecuniary estimates are summed in quadrature. For the projected
collective dose savings, the root quadrature sum yields an overall
relative uncertainty of a factor of 2.3 lower and higher than the modal
point estimates and corresponding respectively to the 5th and 95th
percentiles of a nominal distribution of confidence; for the projected
numbers of lives and years of life spared premature death, the overall
relative uncertainty is a factor of 3.6 lower and higher.
[[Page 76077]]
I. Costs of Implementing the Proposed Regulations
Costs to manufacturers of fluoroscopic and radiographic systems
would increase due to these proposals. FDA would also experience costs
for increased compliance activities. Some costs represent one-time
expenditures to develop new designs or manufacturing processes to
incorporate the regulatory changes. Other costs are the ongoing costs
of providing improved equipment performance and features with each
installed unit. FDA developed unit cost estimates for each required
activity and multiplied the respective unit cost by the relevant
variables in the affected industry segment. One-time costs are
amortized over the estimated useful life of a fluoroscopy system (10
years) using a 7 percent discount rate. This allows costs to be
analyzed as average annualized costs as well as first year
expenditures.
FDA developed these cost estimates based on its experience with the
industry and its knowledge regarding design and manufacturing practices
of the industry. Initially, gross, upper-bound estimates were selected
to ensure that expected costs were adequately addressed. The initial
assumptions and estimates were posted on FDA's Web site and circulated
to the affected industry for comment in July 2000. FDA received no
comments on these initial, upper-bound estimates and therefore believes
that they were generally in line with industry expectations. Since
then, in order to refine the estimates to provide a more accurate
representation of the upper-bound costs of the proposed amendments, FDA
re-examined its estimating assumptions and reduced some unit cost
figures based on the expectation that future economies of scale would
reduce the expense of some required features. This section presents a
brief discussion of the cost estimates. A detailed description of this
analysis is given in Ref. 33.
FDA has no information, indication, or economic presumption that
costs estimated to be borne by manufacturers would be passed on to
purchasers. The cost analysis therefore is limited to those parties who
would be directly affected by the adoption of the proposed amendments,
namely, manufacturers and FDA itself. FDA requests any information on
the costs that would be imposed by these new requirements that would
aid in refining the cost estimates.
1. Costs Associated With Requirements Affecting Equipment Design
The agency estimates that approximately one-half (20) of the
manufacturers of x-ray systems will have to make design and
manufacturing changes to comply with the revised beam quality
requirements. It is estimated that a total of 200 x-ray models would be
affected, with a one-time cost of at most $20,000 per model. These
numbers result in an estimated first year expenditure of $4.0 million
to redesign systems to meet the new beam quality requirement.
It will be necessary for manufacturers of fluoroscopic systems
equipped with x-ray tubes with high heat capacity to redesign some
systems to provide a means to add additional beam filtration. FDA
estimates a design cost of $50,000 per model. A total of 100 models are
likely to be affected for a one-time cost of $5.0 million to
fluoroscopic system manufacturers. In addition, each system would cost
more to manufacture because of the increased costs for components to
provide the added feature. The increased cost of this added feature is
estimated at $1,000 per fluoroscopic system. A total of 650
fluoroscopic systems are estimated to be installed annually with high
heat capacity x-ray tubes, resulting in a total of $0.65 million in
increased annual costs.
Modification of x-ray systems to meet the revised requirement for
field limitation will entail either changes in installation and
adjustment procedures, or redesign of systems. Each fluoroscopic system
would need either modification in the adjustment procedure for the
collimators (for which new installation and adjustment procedures would
be developed at an estimated one-time cost of $20,000 per model) or
collimators would need to be redesigned at an estimated cost of $50,000
per model. FDA has assumed that one-half of all flouroscopic x-ray
system models (5 models each for 20 manufacturers) would need
modifications to meet the new requirement, while the remainder would
either meet the new requirement or could meet it through very minor
modifications in the collimator adjustment procedure. For those system
models not meeting the new requirement, it is assumed that a redesign
of the collimator system is required at a cost of about $50,000 per
model, leading to an upper-bound estimate of the total redesign cost of
$5.0 million (20 manufacturers x 5 models x $50,000). All stationary
fluoroscopic systems would most likely need redesigned collimators that
would add an additional $2,000 per new system due to increased
complexity of the collimator. An annual industry cost increase of $5.0
million accounts for all 2,500 annual installations of systems with
these more expensive collimators.
The proposals to modify the requirement limiting the maximum
entrance AKR and to remove the exception to the limit during recording
of images in analog format using a video recorder will only affect the
adjustment of newly installed systems having such recording capability.
This requirement is not expected to impose significant costs.
FDA is proposing that all fluoroscopic systems include displays of
irradiation time, AKR, and cumulative air kerma to assist operators in
keeping track of patient exposures and avoiding overexposures. Each
model of fluoroscopic system would need to be redesigned (at a maximum
estimated cost of $50,000 per model) for a one-time estimated cost of
$10.0 million (200 models x $50,000). Accessory or add-on equipment for
existing fluoroscopic systems that provide similar information are
currently available for an additional cost of over $10,000 per system.
However, FDA expects the average manufacturing cost of including such a
feature as an integral feature of a fluoroscopic system to be less than
$4,000 per system, due to achievable economies of scale and integration
with other system computer capabilities. This assumption results in
annual cost increases of $16.8 million (4,200 annual installations x
$4,000).
The proposed amendments would require that all newly manufactured
fluoroscopic systems be provided with LIH capability. FDA expects that
10 fluoroscopic system manufacturers would need to redesign their
systems to include this technology at a maximum cost of $100,000 per
manufacturer. Total one-time design costs would equal $1.0 million for
the industry (10 manufacturers x $100,000). It is estimated that about
half of the new systems installed would already be equipped with this
feature. Thus, about half of the newly installed systems that currently
do not provide this feature would need it. FDA estimates that the cost
would be an additional $2,000 for each system required to have this
feature. Thus, annual costs would increase by $4.2 million (2,100
annual systems x $2,000).
The amendment clarifying the requirement for MSSD for small C-arm
systems is anticipated to require redesign of several of these systems.
As there are only three manufacturers of these systems, and the
redesign costs are estimated to be no more than $50,000 per system, the
total one-time cost for this change would be $0.2 million. The
[[Page 76078]]
average annualized cost of this proposed change would be negligible.
In summary, total industry costs for compliance with the amendments
in the area of equipment design include one-time costs of $25.2
million. This total equals an average annualized cost (7 percent
discount rate over 10 years) of $3.6 million. In addition, annual
recurring costs for new equipment features associated with these
proposed provisions are expected to equal $26.7 million.
2. Costs Associated With Additional Information for Users
The proposed amendments would require that additional information
be provided in the user instructions regarding fluoroscopic systems.
FDA has estimated that each model of fluoroscopic system would need a
revised and augmented instruction manual at a cost of less than $5,000
per model. This is equal to a maximum one-time cost of $1.0 million
(200 models of fluoroscopic systems x $5,000) and implies maximum
average annualized costs of $0.14 million. In addition, each newly
installed system would include an improved instruction manual. FDA
estimates a cost of $20 per manual for printing and distribution of the
required additional information. Each of the 4,200 installed
fluoroscopy systems would include a revised manual for an annual cost
of approximately $0.1 million.
Related to the requirements for additional information is the
proposal to change the quantity used to describe the radiation produced
by the x-ray system. Because the change to use of the quantity air
kerma does not require any changes or actions on the part of
manufacturers or users, there is no significant cost associated with
it.
3. Costs Associated With Clarifications and Adaptations to New
Technologies
The new definitions and clarifications of applicability proposed
for the standard do not pose any significant new or additional costs on
manufacturers.
4. FDA Costs Associated With Compliance Activities
FDA costs would increase due to the increased compliance activities
that would result from these proposed regulations. In addition, FDA
would experience implementation costs in developing and publicizing the
new requirements. FDA has estimated that approximately five full-time
equivalent employees (FTEs) would be required to implement the proposed
regulations and conduct training of field inspectors. Using the current
estimate of $117,000 per FTE, the one-time cost of implementation to
FDA is approximately $0.6 million. Amortizing this cost over a 10-year
evaluation period using a 7 percent discount rate results in average
annualized costs of about $0.1 million. Ongoing costs of annual
compliance activities are expected to require about three FTEs, or a
little more than $0.3 million per year.
5. Total Costs of the Proposed Regulation
The estimated costs of the amendments identified as having any
significant cost impact are summarized in table 7 of this document. The
costs are identified as non-recurring costs that must be met initially
or as annual costs associated with continued production of systems
meeting the proposed requirements or additional annual enforcement of
the amendments. The total annualized cost of the proposed regulations
(averaged over 10 years) equals $30.8 million, of which $30.4 million
would be borne by manufacturers. The annualized estimate of $30.8
million represents amortization of first year costs of $53.8 million
and expenditures from years 2 through 10 of $27 million annually.
Table 7.--Summary of Costs of Amendments
----------------------------------------------------------------------------------------------------------------
Non-recurring Costs Annual Costs to
Amendment Described in to Manufacturers ($ Non-recurring Costs Manufacturers ($ Annual Costs to FDA
Section millions) to FDA ($ millions) millions) ($ millions)
----------------------------------------------------------------------------------------------------------------
II.A none 0.0059 none none
----------------------------------------------------------------------------------------------------------------
II.B none 0.0324 none none
----------------------------------------------------------------------------------------------------------------
II.D 1.0 none 0.084 0.0117
----------------------------------------------------------------------------------------------------------------
II.E 9.0 0.0117 0.650 none
----------------------------------------------------------------------------------------------------------------
II.F 5.0 0.0468 5.0 none
----------------------------------------------------------------------------------------------------------------
II.G, II.H, and II.I none none none none
----------------------------------------------------------------------------------------------------------------
II.J 0.150 0.0234 none none
----------------------------------------------------------------------------------------------------------------
II.K 10.0 0.4680 16.8 0.2340
----------------------------------------------------------------------------------------------------------------
II.L 1.0 0.0234 4.2 none
----------------------------------------------------------------------------------------------------------------
Total 26.150 0.6026 26.734 0.2457
----------------------------------------------------------------------------------------------------------------
Therefore, during the first 10 years after the effective date of
the proposed amendments, the average annual cost is estimated to be
$30.8 million, compared to a projected average annual benefits of $320
million, within a range estimated between $88 million and $1.2 billion.
J. Small Business Impacts
FDA believes that it is likely that the proposed rule will have a
significant impact on a substantial number of small entities and has
conducted an IRFA. This analysis is designed to assess the impact of
the proposed rule on small entities and alert any impacted entities of
the expected impact.
1. Description of Impact
The objective of the proposed regulation is to reduce the
likelihood of adverse events due to unnecessary exposure to radiation
during diagnostic x-ray procedures, primarily fluoroscopic procedures.
The amendments would accomplish this by requiring performance features
on all fluoroscopic
[[Page 76079]]
x-ray systems that would protect patients and health personnel while
maintaining image quality.
Manufacturers of diagnostic x-ray systems, including fluoroscopy
equipment, are grouped within the North American Industry
Classification System (NAICS) industry code 334517 (Irradiation
Apparatus Manufacturers)\1\. The Small Business Administration (SBA)
classifies as ``small'' any entity with 500 or fewer employees within
this industry. Relatively small numbers of employees typify firms
within this NAICS code group. About one-half of the establishments
within this industry employ fewer than 20 workers, and companies have
an average of 1.2 establishments per company. The manufacturers are
relatively specialized, with about 84 percent of company sales coming
from within the affected industry. In addition, 97 percent of all
shipments of irradiation equipment originate by manufacturers
classified within this industry.
---------------------------------------------------------------------------
\1\NAICS has replaced the Standard Industrial Classification
(SIC) codes. NAICS Industry Group 334517 (Irradiation Apparatus)
coincides with SIC Group 3844 (X-Ray Apparatus and Tubing).
---------------------------------------------------------------------------
The Manufacturing Industry Series report on Irradiation Apparatus
Manufacturing for NAICS code 334517 from the 1997 Economic Census
indicates 136 companies having 154 establishments for this industry in
the United States. This report also indicates that only 15 of these
establishments have 250 or more employees, with only 5 establishments
having more than 500 employees. Therefore, this industry sector is
predominately composed of firms meeting the SBA description of a
``small entity.'' Of the total value of shipments of $3,797,837,000 for
this industry, 73 percent are from the 15 establishments with 250 or
more employees. Thus, for the purposes of the IRFA, most of the
diagnostic x-ray equipment manufacturing firms that will be affected by
these proposed amendments are small entities.
The impact of the proposed amendments will be similar on
manufacturers of diagnostic x-ray systems, whether or not they are
small entities. This impact is the increased costs to design and
manufacture x-ray systems that meet the new requirements. For those
manufacturers that produce smaller numbers of systems per year, the
impact of the cost of system redesign to meet the new requirements will
result in a greater per unit cost impact than for manufacturers with a
high volume of unit sales over which the development costs may be
spread. This may have a disproportionate impact on the very small firms
with a low volume of sales.
FDA considered whether there were approaches that could be taken to
mitigate this impact on the firms producing the smaller numbers of
systems. FDA, however, identified no feasible way to do this and also
accomplish the needed public health protection. The proposed radiation-
safety-related requirements are appropriate for any x-ray system,
independent of the circumstances of the manufacturer. FDA considers it
appropriate for any firm producing x-ray systems to provide the level
of radiation protection that will be afforded by the revised standard.
Patients receiving x-ray examinations or procedures warrant the same
degree of radiation safety regardless of the circumstances of the
manufacturer of the equipment.
2. Analysis of Alternatives
FDA examined and rejected several alternatives to proposing
amendments to the performance standard. One alternative was to take no
actions to modify the standard. This option was rejected because it
would not permit clarification of the manner in which the standard
should be applied to the technological changes occurring with
fluoroscopic x-ray system design and function. This option was also
rejected as failing to meet the public expectation that the federal
performance standard assures adequate radiation safety performance and
features for fluoroscopic x-ray systems. The changes that have occurred
since the standard was developed in the early 1970s necessitate
modification of the standard to reflect current technology and to
recognize the increased radiation hazards posed by new fluoroscopic
techniques and procedures.
A portion of the concern and the unnecessary radiation exposure
resulting from current fluoroscopic practices might be addressed
through the establishment of controls and requirements regarding the
qualifications and training of physicians permitted or allowed to use
fluoroscopic systems. Such requirements could assure that, contrary to
the current situation, all physicians using fluoroscopy are adequately
trained regarding radiation safety practices, proper fluoroscopic
system use, and methods for assuring that patient doses are maintained
as low as possible. This alternative was rejected because FDA does not
have the authority, under current law, to establish such requirements.
To be effective, such a program would have to be established by States
or medical professional societies or certification bodies. While
recognizing that encouragement of such activities by FDA is worthwhile,
reliance on such efforts alone would not result in the needed
performance improvement of fluoroscopic x-ray systems. FDA concluded
that improved use of fluoroscopy requires the dose reduction features
and operator feedback mechanism regarding patient doses that would be
provided by the proposed amendments.
Alternatives to the specific amendments proposed were also
considered in developing these proposals. These alternatives are
described in detail in the assessment report developed and filed as
part of the information supporting these amendments (Ref. 33). FDA
requests comments on alternatives to these proposed amendments that
would accomplish the needed public health protection and, in
particular, any alternatives that could mitigate the impact of the
proposed amendments on small businesses.
3. Ensuring Small Entity Participation in Rulemaking
FDA believes it is possible that the proposed regulation could have
a significant impact on small entities. The impact would occur due to
increased design and production costs for fluoroscopy systems. FDA
solicits comment on the nature of this impact and whether there are
reasonable alternatives that might accomplish the intended public
health goals.
The proposed regulation will be available on the Internet at http://www.fda.gov
for review by all interested parties, and all comments
will be considered prior to final implementation of the regulation. In
addition, FDA will communicate the proposed regulation to manufacturer
organizations and trade associations as well as parties that have
previously indicated an interest in amendments to the diagnostic x-ray
equipment performance standard. The proposed amendments will also be
brought to the attention of relevant medical professional societies and
organizations whose members are likely to use fluoroscopic x-ray
systems. FDA will solicit the assistance of the SBA during the comment
period to assure that all small manufacturers impacted by the proposed
amendments are aware of the opportunity to comment on the proposal,
possible alternatives and its impact.
[[Page 76080]]
K. Reporting Requirements and Duplicate Rules
FDA has concluded that the proposed rule imposes new reporting and
other compliance requirements on small businesses. In addition, FDA has
identified no relevant Federal rules that may duplicate, overlap, or
conflict with the proposed rule. The cost in the labeling is addressed
previously.
L. Conclusion of the Analysis of Impacts
FDA has examined the impacts of the proposed amendments to the
performance standard. Based on this evaluation, an upper-bound estimate
has been made for average annualized costs amounting to $30.8 million,
of which $30.4 million would be borne by the manufacturers of this
equipment. FDA believes that the reductions in acute and long-term
radiation injuries to patients that would be facilitated by the
proposed amendments would appreciably outweigh the upper-bound costs
estimated for compliance with the rules. Finally, FDA has concluded
that it is likely that this proposal would have a significant impact on
a substantial number of small entities.
FDA solicits comment on all aspects of this analysis and all
assumptions used.
VII. Federalism
FDA has analyzed this proposed rule in accordance with the
principles set forth in Executive Order 13132. FDA has determined that
the proposed rule does not contain policies that have substantial
direct effect on the States, on the relationship between the National
Government and the States, or on the distribution of power and
responsibilities among the various levels of government. Accordingly,
the agency has concluded that the rule does not contain policies that
have federalism implications as defined in the Executive order and,
consequently, a federalism summary impact statement is not required.
VIII. Submission of Comments
Interested persons may submit to the Dockets Management Branch (see
ADDRESSES) written or electronic comments regarding this proposal. Two
copies of any mailed comments are to be submitted, except that
individuals may submit one copy. Comments are to be identified with the
docket number found in brackets in the heading of this document.
Received comments may be seen in the Dockets Management Branch between
9 a.m. and 4 p.m., Monday through Friday.
IX. References
The following references have been placed on display in the Dockets
Management Branch (see ADDRESSES) and may be seen by interested persons
between 9 a.m. and 4 p.m., Monday through Friday.
1. Allisy, A. et al., ``Fundamental Quantities and Units for
Ionizing Radiation,'' ICRU Report No. 60, International Commission
on Radiation Units and Measurements, Bethesda, MD, December 1998.
2. FDA Guidance Document, ``Guidance for the Submission of
510(k)s for Solid State X-Ray Imaging Devices,'' Food and Drug
Administration, August 6, 1999.
3. National Council on Radiation Protection and Measurements,
``Medical X-Ray and Gamma-Ray Protection for Energies Up to 10 MeV,
Equipment Design and Use,'' NCRP Report No. 33, Bethesda, MD,
February 1, 1968.
4. International Standard, International Electrotechnical
Commission (IEC) 601-1-3, ``Medical Electrical Equipment--Part 1:
General Requirements for Safety. 3. Collateral Standard: General
Requirements for Radiation Protection in Diagnostic X-Ray
Equipment,'' 1994.
5. Cranley, K., B. J. Gilmore, and G. W. A. Fogarty, ``Data for
Estimating X-Ray Tube Total Filtration,'' Institute of Physical
Sciences in Medicine, Report No. 64, Institute of Physical Sciences
in Medicine, York, England, 1991.
6. Shope, T. B., ``Radiation-Induced Skin Injuries From
Fluoroscopy,'' RadioGraphics, vol. 16, pp. 1195-1199, September
1996.
7. Gagne, R. M., P. W. Quinn, and R. J. Jennings, ``Comparison
of Beam-Hardening and K-Edge Filters for Imaging Barium and Iodine
During Fluoroscopy,'' Medical Physics, vol. 21, pp. 107-121, 1994.
8. Proceedings of the ACR/FDA Workshop on Fluoroscopy,
``Strategies for Improvement in Performance, Radiation Safety and
Control,'' Dulles Hyatt Hotel, Washington, DC, October 16 and 17,
1992, American College of Radiology, Merrifield, VA, 1993.
9. Stern, S. H. et al., ``Handbook of Selected Tissue Doses for
Fluoroscopic and Cineangiographic Examination of the Coronary
Arteries,'' HHS Publication FDA 95-8288, U.S. Department of Health
and Human Services, Public Health Service, Food and Drug
Administration, Center for Devices and Radiological Health,
Rockville, MD, 1995.
10. Rudin, S. and D. R. Bednarek, ``Spatial Shaping of the Beam:
Collimation, Grids, Equalization Filters, and Region-of-Interest
Fluoroscopy,'' A Categorical Course in Physics, Physical and
Technical Aspects of Angiography and Interventional Radiology
(syllabus). Eds. S. Balter and T. B. Shope, presented at the 81st
Scientific Assembly and Annual Meeting of the Radiological Society
of North America, Chicago, IL, November 1995.
11. Solomon, E. et al., ``Low-Exposure Scanning-Beam X-Ray
Fluoroscopy System,'' SPIE, vol. 2708, pp. 140-149, 1996.
12. National Council on Radiation Protection and Measurements,
``Quality Assurance for Diagnostic Imaging Equipment,'' NCRP Report
No. 99, Bethesda, MD, December 30, 1988.
13. National Council on Radiation Protection and Measurements,
``Medical X-Ray, Electron Beam and Gamma-Ray Protection for Energies
up to 50 MeV,'' NCRP Report No. 102, Bethesda, MD, June 30, 1989.
14. Beninson, D. et al., ``1990 Recommendations of the
International Commission on Radiological Protection,'' Annals of the
ICRP, ICRP Publication 60, vol. 21, Nos. 1-3, Pergamon Press,
Oxford, UK, 1991.
15. Thornbury, J. R. et al., ``An Introduction to Efficacy in
Diagnostic Radiology and Nuclear Medicine (Justification of Medical
Radiation Exposure),'' NCRP Commentary No. 13, National Council on
Radiation Protection and Measurement, Bethesda, MD, August 1995.
16. Zuur, C. and F. Mettler, ``Radiological Protection and
Safety in Medicine,'' Annals of the ICRP, ICRP Publication 73, vol.
26, No. 2, Pergamon Press, Oxford, UK, 1996.
17. ``Council Directive 97/43/Euratom of 30 June 1997 on Health
Protection of Individuals Against the Dangers of Ionizing Radiation
in Relation to Medical Exposure, and Repealing Directive 84/466/
Euratom,'' Official Journal of the European Communities, No. L 180,
pp. 22-27, July 9, 1997.
18. Food and Drug Administration, ``Avoidance of Serious X-Ray-
Induced Skin Injuries to Patients During Fluoroscopically-Guided
Procedures,'' Food and Drug Administration Important Information for
Physicians and Other Health Care Professionals, September 9, 1994.
19. Food and Drug Administration, ``Avoidance of Serious X-Ray-
Induced Skin Injuries to Patients During Fluoroscopically-Guided
Procedures,'' FDA Public Health Advisory, September 30, 1994.
20. Food and Drug Administration, ``Recording Information in the
Patient's Medical Record That Identifies the Potential for Serious
X-Ray-Induced Skin Injuries Following Fluoroscopically-Guided
Procedures,'' Food and Drug Administration Important Information for
Physicians and Other Health Care Professionals, September 15, 1995.
21. Rosenstein, M. et al., ``Handbook of Selected Tissue Doses
for the Upper Gastrointestinal Fluoroscopic Examination,'' U.S.
Department of Health and Human Services, Public Health Service, Food
and Drug Administration, Center for Devices and Radiological Health,
FDA Publication 92-8282, Rockville, MD, 1992.
22. Upton, A. C. et al., ``Health Effects of Exposure to Low
Levels of Ionizing Radiation: BEIR V,'' Committee on the Biological
Effects of Ionizing Radiations, Board on Radiation Effects Research,
Commission on Life Sciences, National Research Council, National
Academy of Science, National Academy Press, Washington, DC, 1990.
23. B[auml]uml, A. et al., Eds., Proceedings of the ``Joint WHO/
ISH Workshop on Efficacy and Radiation Safety Interventional
Radiology,'' Munich-Neuherberg, Germany, October 9 to 13, 1995, BfS-
ISH Report 178/
[[Page 76081]]
97, Bundesamt f[uuml]r Strahlenschutz, Fachbereich Strahlenhygiene,
Institut f[uuml]r Strahlenhygiene, Neuherberg, Germany, 1997.
24. International Standard, International Electrotechnical
Commission (IEC) 60601-2-43, ``Medical Electrical Equipment-Part 2-
43: Particular Requirements for the Safety of X-Ray Equipment for
Interventional Procedures,'' edition 1, 2000.
25. Gkanatsios, N. A. et al., ``Evaluation of an On-Line Patient
Exposure Meter in Neuroradiology,'' Radiology, vol. 203, pp. 837-
842, 1997.
26. Geise, R. A. et al., ``Radiation Doses During Pediatric
Radiofrequency Catheter Ablation Procedures,'' PACE, Part 1, vol.
19, pp. 1605-1611, 1996.
27. Transcript of Proceedings, Twenty-fifth Meeting of the
Technical Electronic Product Radiation Safety Standards Committee,
vol. 1, pp. 118-121, Gaithersburg, MD, September, 1998.
28. Suleiman, O. H. et al., ``Nationwide Survey of Fluoroscopy:
Radiation Dose and Image Quality,'' Radiology, vol. 203, pp. 471-
476, 1997.
29. Stern, S. H. et al., ``Estimated Benefits of Proposed
Amendments to the FDA Radiation-Safety Standard for Diagnostic X-ray
Equipment,'' Poster presented at the 2001 FDA Science Forum,
Washington, DC, February 15-16, 2001. Also available at http://www.fda.gov/cdrh/radhlth/021501
xray.html.
30. Rosenstein, M. et al., Committee on Interagency Radiation
Research and Policy Coordination Science Panel Report No. 9, ``Use
of BIER V and UNSCEAR 1988 in Radiation Risk Assessment, Lifetime
Total Cancer Mortality Risk Estimates at Low Doses and Low Dose
Rates for Low-LET Radiation,'' (ORAU 92/F-64), OSTP, EOP,
Washington, DC, December 1992.
31. ``Sources and Effects of Ionizing Radiation,'' United
Nations Scientific Committee on the Effects of Atomic Radiation,
UNSCEAR 2000 Report to the General Assembly, with Scientific
Annexes, New York: United Nations, 2000.
32. National Council on Radiation Protection and Measurements,
``Evaluation of the Linear-Nonthreshold Dose-Response Model for
Ionizing Radiation,'' NCRP Report 136, Bethesda, MD, June 2001.
33. ``Assessment of the Impact of the Proposed Amendments to the
Performance Standard for Diagnostic X-Ray Equipment Addressing
Fluoroscopic X-ray Systems,'' Food and Drug Administration, pp. 1-
28, November 15, 2000. Also available at http://www.fda.gov/cdrh/radhealth/fluoro/amendxrad.html
List of Subjects in 21 CFR Part 1020
Electronic products, Medical devices, Radiation protection,
Reporting and recordkeeping requirements, Television, X-rays.
Therefore, under the Federal Food, Drug, and Cosmetic Act, and
under authority delegated to the Commissioner of Food and Drugs, it is
proposed that 21 CFR part 1020 be amended as follows:
PART 1020--PERFORMANCE STANDARDS FOR IONIZING RADIATION EMITTING
PRODUCTS
1. The authority citation for 21 CFR part 1020 continues to read as
follows:
Authority: 21 U.S.C. 351, 352, 360e-360j, 360gg-360ss, 371, 381.
2. Revise Sec. 1020.30 to read as follows:
Sec. 1020.30 Diagnostic x-ray systems and their major components.
(a) Applicability--(1) The provisions of this section are
applicable to:
(i) The following components of diagnostic x-ray systems:
(A) Tube housing assemblies, x-ray controls, x-ray high-voltage
generators, x-ray tables, cradles, film changers, vertical cassette
holders mounted in a fixed location and cassette holders with front
panels, and beam-limiting devices manufactured after August 1, 1974.
(B) Fluoroscopic imaging assemblies manufactured after August 1,
1974, and before April 26, 1977.
(C) Spot-film devices and image intensifiers manufactured after
April 26, 1977.
(D) Cephalometric devices manufactured after February 25, 1978.
(E) Image receptor support devices for mammographic x-ray systems
manufactured after September 5, 1978.
(F) Image receptors which are electrically powered or connected
with the x-ray system manufactured on or after [date 1 year after date
of publication of the final rule in the Federal Register].
(ii) Diagnostic x-ray systems, except computed tomography x-ray
systems, incorporating one or more of such components; however, such x-
ray systems shall be required to comply only with those provisions of
this section and Sec. Sec. 1020.31 and 1020.32, which relate to the
components certified in accordance with paragraph (c) of this section
and installed into the systems.
(iii) Computed tomography (CT) x-ray systems manufactured before
November 29, 1984.
(iv) CT gantries manufactured after September 3, 1985.
(2) The following provisions of this section and Sec. 1020.33 are
applicable to CT x-ray systems manufactured or remanufactured on or
after November 29, 1984:
(i) Section 1020.30(a);
(ii) Section 1020.30(b) ``Technique factors'';
(iii) Section 1020.30(b) ``CT,'' ``Dose,'' ``Scan,'' ``Scan time,''
and ``Tomogram'';
(iv) Section 1020.30(h)(3)(vi) through (h)(3)(viii);
(v) Section 1020.30(n);
(vi) Section 1020.33(a) and (b);
(vii) Section 1020.33(c)(1) as it affects Sec. 1020.33(c)(2); and
(viii) Section 1020.33(c)(2).
(3) The provisions of this section and Sec. 1020.33 in its
entirety, including those provisions in paragraph (a)(2) of this
section, are applicable to CT x-ray systems manufactured or
remanufactured on or after September 3, 1985. The date of manufacture
of the CT system is the date of manufacture of the CT gantry.
(b) Definitions. As used in this section and Sec. Sec. 1020.31,
1020.32, and 1020.33, the following definitions apply:
Accessible surface means the external surface of the enclosure or
housing provided by the manufacturer.
Accessory component means:
(1) A component used with diagnostic x-ray systems, such as a
cradle or film changer, that is not necessary for the compliance of the
system with applicable provisions of this subchapter but which requires
an initial determination of compatibility with the system; or
(2) A component necessary for compliance of the system with
applicable provisions of this subchapter but which may be interchanged
with similar compatible components without affecting the system's
compliance, such as one of a set of interchangeable beam-limiting
devices; or
(3) A component compatible with all x-ray systems with which it may
be used and that does not require compatibility or installation
instructions, such as a tabletop cassette holder.
Air kerma means kerma in air (see kerma).
Aluminum equivalent means the thickness of aluminum (type 1100
alloy)\1\ affording the same attenuation, under specified conditions as
the material in question.
---------------------------------------------------------------------------
\1\The nominal chemical composition of type 1100 aluminum alloy
is 99.00 percent minimum aluminum, 0.12 percent copper, as given in
``Aluminum Standards and Data'' (1969). Copies may be obtained from
The Aluminum Association, New York, NY.
---------------------------------------------------------------------------
Articulated joint means a joint between two separate sections of a
tabletop which joint provides the capacity for one of the sections to
pivot on the line segment along which the sections join.
Assembler means any person engaged in the business of assembling,
replacing, or installing one or more components into a diagnostic x-ray
system or subsystem. The term includes the owner of an x-ray system or
his or her employee or agent who assembles components into an x-ray
system that is
[[Page 76082]]
subsequently used to provide professional or commercial services.
Attenuation block means a block or stack of type 1100 aluminum
alloy or aluminum alloy having equivalent attenuation with dimensions
20 centimeters by 20 centimeters by 3.8 centimeters.
Automatic exposure control (AEC) means a device which automatically
controls one or more technique factors in order to obtain at a
preselected location(s) a required quantity of radiation.
Automatic exposure rate control (AERC) means a device which
automatically controls one or more technique factors in order to obtain
at a preselected location(s) a required quantity of radiation per unit
time.
Beam axis means a line from the source through the centers of the
x-ray fields.
Beam-limiting device means a device which provides a means to
restrict the dimensions of the x-ray field.
Cantilevered tabletop means a tabletop designed such that the
unsupported portion can be extended at least 100 centimeters beyond the
support.
Cassette holder means a device, other than a spot-film device, that
supports and/or fixes the position of an x-ray film cassette during an
x-ray exposure.
Cephalometric device means a device intended for the radiographic
visualization and measurement of the dimensions of the human head.
Coefficient of variation means the ratio of the standard deviation
to the mean value of a population of observations. It is estimated
using the following equation:
[GRAPHIC] [TIFF OMITTED] TP10DE02.059
where:
s = Estimated standard deviation of the population.
X = Mean value of observations in sample.
Xi = ith observation sampled.
n = Number of observations sampled.
Computed tomography (CT) means the production of a tomogram by the
acquisition and computer processing of x-ray transmission data.
Control panel means that part of the x-ray control upon which are
mounted the switches, knobs, pushbuttons, and other hardware necessary
for manually setting the technique factors.
Cooling curve means the graphical relationship between heat units
stored and cooling time.
Cradle means:
(1) A removable device which supports and may restrain a patient
above an x-ray table; or
(2) A device;
(i) Whose patient support structure is interposed between the
patient and the image receptor during normal use;
(ii) Which is equipped with means for patient restraint; and
(iii) Which is capable of rotation about its long (longitudinal)
axis.
CT gantry means tube housing assemblies, beam-limiting devices,
detectors, and the supporting structures, frames, and covers which hold
and/or enclose these components.
Diagnostic source assembly means the tube housing assembly with a
beam-limiting device attached.
Diagnostic x-ray system means an x-ray system designed for
irradiation of any part of the human body for the purpose of diagnosis
or visualization.
Dose means the absorbed dose as defined by the International
Commission on Radiation Units and Measurements. The absorbed dose, D,
is the quotient of d[egr] by dm, where d[egr] is the mean energy
imparted to matter of mass dm; thus D=d[egr]/dm, in units of J/kg,
where the special name for the unit of absorbed dose is gray (Gy).
Equipment means x-ray equipment.
Exposure (X) means the quotient of dQ by dm where dQ is the
absolute value of the total charge of the ions of one sign produced in
air when all the electrons and positrons liberated or created by
photons in air of mass dm are completely stopped in air; thus X=dQ/dm,
in units of C/kg.
Field emission equipment means equipment which uses an x-ray tube
in which electron emission from the cathode is due solely to action of
an electric field.
Fluoroscopic imaging assembly means a subsystem in which x-ray
photons produce a set of fluoroscopic images or radiographic images
recorded from the fluoroscopic image receptor. It includes the image
receptor(s), electrical interlocks, if any, and structural material
providing linkage between the image receptor and diagnostic source
assembly.
Fluoroscopy means a technique for generating x-ray images and
presenting them instantaneously and continuously as visible images for
the purpose of providing the user with a visual display of dynamic
processes.
General purpose radiographic x-ray system means any radiographic x-
ray system which, by design, is not limited to radiographic examination
of specific anatomical regions.
Half-value layer (HVL) means the thickness of specified material
which attenuates the beam of radiation to an extent such that the AKR
is reduced to one-half of its original value. In this definition the
contribution of all scattered radiation, other than any which might be
present initially in the beam concerned, is deemed to be excluded.
Image intensifier means a device, installed in its housing, which
instantaneously converts an x-ray pattern into a corresponding light
image of higher energy density.
Image receptor means any device, such as a fluorescent screen,
radiographic film, x-ray image intensifier tube, solid-state detector,
or gaseous detector, which transforms incident x-ray photons either
into a visible image or into another form which can be made into a
visible image by further transformations. In those cases where means
are provided to preselect a portion of the image receptor, the term
``image receptor'' shall mean the preselected portion of the device.
Image receptor support device means, for mammography x-ray systems,
that part of the system designed to support the image receptor during a
mammographic examination and to provide a primary protective barrier.
Isocenter means the center of the smallest sphere through which the
beam axis passes for a C-arm gantry moving through a full range of
rotations about a common center.
Kerma means the quantity as defined by the International Commission
on Radiation Units and Measurements. The kerma, K, is the quotient of
dEtr by dm, where dEtr is the sum of the initial
kinetic energies of all the charged particles liberated by uncharged
particles in a mass dm of material; thus K=dEtr/dm, in units
of J/kg, where the special name for the unit of kerma is gray (Gy).
When the material is air, the quantity is referred to as ``air kerma.''
Last-image hold (LIH) radiograph means an image obtained either by
retaining one or more fluoroscopic images, which may be temporally
integrated, at the end of a fluoroscopic exposure or by initiating a
separate and distinct radiographic exposure automatically and
immediately in conjunction with termination of the fluoroscopic
exposure.
Lateral fluoroscope means the x-ray tube and image receptor
combination in a biplane system dedicated to the lateral projection. It
consists of the lateral x-ray tube housing assembly and the lateral
image receptor that are fixed in position relative to the table with
the x-ray beam axis parallel to the plane of the table.
[[Page 76083]]
Leakage radiation means radiation emanating from the diagnostic
source assembly except for:
(1) The useful beam; and
(2) Radiation produced when the exposure switch or timer is not
activated.
Leakage technique factors means the technique factors associated
with the diagnostic source assembly which are used in measuring leakage
radiation. They are defined as follows:
(1) For diagnostic source assemblies intended for capacitor energy
storage equipment, the maximum-rated peak tube potential and the
maximum-rated number of exposures in an hour for operation at the
maximum-rated peak tube potential with the quantity of charge per
exposure being 10 millicoulombs (or 10 mAs) or the minimum obtainable
from the unit, whichever is larger;
(2) For diagnostic source assemblies intended for field emission
equipment rated for pulsed operation, the maximum-rated peak tube
potential and the maximum-rated number of x-ray pulses in an hour for
operation at the maximum-rated peak tube potential; and
(3) For all other diagnostic source assemblies, the maximum-rated
peak tube potential and the maximum-rated continuous tube current for
the maximum-rated peak tube potential.
Light field means that area of the intersection of the light beam
from the beam-limiting device and one of the set of planes parallel to
and including the plane of the image receptor, whose perimeter is the
locus of points at which the illuminance is one-fourth of the maximum
in the intersection.
Line-voltage regulation means the difference between the no-load
and the load line potentials expressed as a percent of the load line
potential; that is,
Percent line-voltage regulation = 100(Vn - Vi) /
Vi
where:
Vn = No-load line potential and
Vi = Load line potential.
Maximum line current means the root mean square current in the
supply line of an x-ray machine operating at its maximum rating.
Mode of operation means, for fluoroscopic systems, a distinct
method of fluoroscopy or radiography selected with a set of technique
factors or other control settings uniquely associated with the mode.
Examples of distinct modes of operation include normal fluoroscopy
(analog or digital), high-level control fluoroscopy, cineradiography
(analog), digital cineradiography, digital subtraction angiography,
electronic radiography using the fluoroscopic image receptor, and
photospot recording. In a specific mode of operation, certain system
variables affecting air kerma, AKR, or image quality, such as image
magnification, x-ray field size, pulse rate, pulse duration, number of
pulses per exposure series, SID, or optical aperture, may be adjustable
or may vary; their variation per se does not comprise a mode of
operation different from the one that has been selected.
Movable tabletop means a tabletop which, when assembled for use, is
capable of movement with respect to its supporting structure within the
plane of the tabletop.
Nonimage-intensified fluoroscopy means fluoroscopy using only a
fluorescent screen.
Peak tube potential means the maximum value of the potential
difference across the x-ray tube during an exposure.
Primary protective barrier means the material, excluding filters,
placed in the useful beam to reduce the radiation exposure for
protection purposes.
Pulsed mode means operation of the x-ray system such that the x-ray
tube current is pulsed by the x-ray control to produce one or more
exposure intervals of duration less than one-half second.
Quick change x-ray tube means an x-ray tube designed for use in its
associated tube housing such that:
(1) The tube cannot be inserted in its housing in a manner that
would result in noncompliance of the system with the requirements of
paragraphs (k) and (m) of this section;
(2) The focal spot position will not cause noncompliance with the
provisions of this section or Sec. 1020.31 or Sec. 1020.32;
(3) The shielding within the tube housing cannot be displaced; and
(4) Any removal and subsequent replacement of a beam-limiting
device during reloading of the tube in the tube housing will not result
in noncompliance of the x-ray system with the applicable field
limitation and alignment requirements of Sec. Sec. 1020.31 and 1020.32.
Radiation therapy simulation system means a radiographic or
fluoroscopic x-ray system intended for localizing the volume to be
exposed during radiation therapy and confirming the position and size
of the therapeutic irradiation field.
Radiography means a technique for generating and recording an x-ray
pattern for the purpose of providing the user with an image(s) after
termination of the exposure.
Rated line voltage means the range of potentials, in volts, of the
supply line specified by the manufacturer at which the x-ray machine is
designed to operate.
Rated output current means the maximum allowable load current of
the x-ray high-voltage generator.
Rated output voltage means the allowable peak potential, in volts,
at the output terminals of the x-ray high-voltage generator.
Rating means the operating limits specified by the manufacturer.
Recording means producing a retrievable form of an image resulting
from x-ray photons.
Scan means the complete process of collecting x-ray transmission
data for the production of a tomogram. Data may be collected
simultaneously during a single scan for the production of one or more
tomograms.
Scan time means the period of time between the beginning and end of
x-ray transmission data accumulation for a single scan.
Solid state x-ray imaging device means an assembly, typically in a
rectangular panel configuration, consisting of:
(1) A transducer layer that intercepts x-ray photons and through a
single or multistage process converts the photon energy into a
modulated signal representative of the x-ray image, and
(2) A matrix of integration and switching elements that are coupled
to the transducer layer. An electrical signal representing the x-ray
image is generated by a charge generation and transfer process within
the integration and switching matrix. The electrical signals may
undergo analog-to-digital conversion before leaving the panel to
provide either a digital radiographic or fluoroscopic image.
Source means the focal spot of the x-ray tube.
Source-image receptor distance (SID) means the distance from the
source to the center of the input surface of the image receptor.
Source-skin distance (SSD) means the distance from the source to
the center of the entrant x-ray field in the plane tangent to the
patient skin surface.
Spot-film device means a device intended to transport and/or
position a radiographic image receptor between the x-ray source and
fluoroscopic image receptor. It includes a device intended to hold a
cassette over the input end of the fluoroscopic image receptor for the
purpose of producing a radiograph.
Stationary tabletop means a tabletop which, when assembled for use,
is incapable of movement with respect to
[[Page 76084]]
its supporting structure within the plane of the tabletop.
Technique factors means the following conditions of operation:
(1) For capacitor energy storage equipment, peak tube potential in
kilovolts (kV) and quantity of charge in milliamperes-seconds (mAs);
(2) For field emission equipment rated for pulsed operation, peak
tube potential in kV and number of x-ray pulses;
(3) For CT equipment designed for pulsed operation, peak tube
potential in kV, scan time in seconds, and either tube current in
milliamperes (mA), x-ray pulse width in seconds, and the number of x-
ray pulses per scan, or the product of the tube current, x-ray pulse
width, and the number of x-ray pulses in mAs;
(4) For CT equipment not designed for pulsed operation, peak tube
potential in kV, and either tube current in mA and scan time in
seconds, or the product of tube current and exposure time in mAs and
the scan time when the scan time and exposure time are equivalent; and
(5) For all other equipment, peak tube potential in kV, and either
tube current in mA and exposure time in seconds, or the product of tube
current and exposure time in mAs.
Tomogram means the depiction of the x-ray attenuation properties of
a section through a body.
Tube means an x-ray tube, unless otherwise specified.
Tube housing assembly means the tube housing with tube installed.
It includes high-voltage and/or filament transformers and other
appropriate elements when they are contained within the tube housing.
Tube rating chart means the set of curves which specify the rated
limits of operation of the tube in terms of the technique factors.
Useful beam means the radiation which passes through the tube
housing port and the aperture of the beam-limiting device when the
exposure switch or timer is activated.
Variable-aperture beam-limiting device means a beam-limiting device
which has the capacity for stepless adjustment of the x-ray field size
at a given SID.
Visible area means the portion of the input surface of the image
receptor over which incident x-ray photons are producing a visible
image.
X-ray control means a device which controls input power to the x-
ray high-voltage generator and/or the x-ray tube. It includes equipment
such as timers, phototimers, automatic brightness stabilizers, and
similar devices, which control the technique factors of an x-ray
exposure.
X-ray equipment means an x-ray system, subsystem, or component
thereof. Types of x-ray equipment are as follows:
(1) Mobile x-ray equipment means x-ray equipment mounted on a
permanent base with wheels and/or casters for moving while completely
assembled;
(2) Portable x-ray equipment means x-ray equipment designed to be
hand-carried; and
(3) Stationary x-ray equipment means x-ray equipment which is
installed in a fixed location.
X-ray field means that area of the intersection of the useful beam
and any one of the set of planes parallel to and including the plane of
the image receptor, whose perimeter is the locus of points at which the
AKR is one-fourth of the maximum in the intersection.
X-ray high-voltage generator means a device which transforms
electrical energy from the potential supplied by the x-ray control to
the tube operating potential. The device may also include means for
transforming alternating current to direct current, filament
transformers for the x-ray tube(s), high-voltage switches, electrical
protective devices, and other appropriate elements.
X-ray system means an assemblage of components for the controlled
production of x-rays. It includes minimally an x-ray high-voltage
generator, an x-ray control, a tube housing assembly, a beam-limiting
device, and the necessary supporting structures. Additional components
which function with the system are considered integral parts of the
system.
X-ray subsystem means any combination of two or more components of
an x-ray system for which there are requirements specified in this
section and Sec. Sec. 1020.31 and 1020.32.
X-ray table means a patient support device with its patient support
structure (tabletop) interposed between the patient and the image
receptor during radiography and/or fluoroscopy. This includes, but is
not limited to, any stretcher equipped with a radiolucent panel and any
table equipped with a cassette tray (or bucky), cassette tunnel,
fluoroscopic image receptor, or spot-film device beneath the tabletop.
X-ray tube means any electron tube which is designed for the
conversion of electrical energy into x-ray energy.
(c) Manufacturers' responsibility. Manufacturers of products
subject to Sec. Sec. 1020.30 through 1020.33 shall certify that each
of their products meet all applicable requirements when installed into
a diagnostic x-ray system according to instructions. This certification
shall be made under the format specified in Sec. 1010.2 of this
chapter. Manufacturers may certify a combination of two or more
components if they obtain prior authorization in writing from the
Director of the Office of Compliance of the Center for Devices and
Radiological Health. Manufacturers shall not be held responsible for
noncompliance of their products if that noncompliance is due solely to
the improper installation or assembly of that product by another
person; however, manufacturers are responsible for providing assembly
instructions adequate to assure compliance of their components with the
applicable provisions of Sec. Sec. 1020.30 through 1020.33.
(d) Assemblers' responsibility. An assembler who installs one or
more components certified as required by paragraph (c) of this section
shall install certified components that are of the type required by
Sec. 1020.31, Sec. 1020.32, or Sec. 1020.33 and shall assemble,
install, adjust, and test the certified components according to the
instructions of their respective manufacturers. Assemblers shall not be
liable for noncompliance of a certified component if the assembly of
that component was according to the component manufacturer's
instruction.
(1) Reports of assembly. All assemblers who install certified
components shall file a report of assembly, except as specified in
paragraph (d)(2) of this section. The report will be construed as the
assembler's certification and identification under Sec. Sec. 1010.2
and 1010.3 of this chapter. The assembler shall affirm in the report
that the manufacturer's instructions were followed in the assembly or
that the certified components as assembled into the system meet all
applicable requirements of Sec. Sec. 1020.30 through 1020.33. All
assembler reports must be on a form prescribed by the Director, Center
for Devices and Radiological Health. Completed reports must be
submitted to the Director, the purchaser, and, where applicable, to the
State agency responsible for radiation protection within 15 days
following completion of the assembly.
(2) Exceptions to reporting requirements. Reports of assembly need
not be submitted for any of the following:
(i) Reloaded or replacement tube housing assemblies that are
reinstalled in or newly assembled into an existing x-ray system;
(ii) Certified accessory components that have been identified as
such to the Center for Devices and Radiological Health in the report
required under Sec. 1002.10 of this chapter;
(iii) Repaired components, whether or not removed from the system
and
[[Page 76085]]
reinstalled during the course of repair, provided the original
installation into the system was reported; or
(iv)(A) Components installed temporarily in an x-ray system in
place of components removed temporarily for repair, provided the
temporarily installed component is identified by a tag or label bearing
the following information:
Temporarily Installed Component
This certified component has been assembled, installed,
adjusted, and tested by me according to the instructions provided by
the manufacturer.
Signature
Company Name
Street Address, P.O. Box
City, State, Zip Code
Date of Installation
(B) The replacement of the temporarily installed component by a
component other than the component originally removed for repair shall
be reported as specified in paragraph (d)(1) of this section.
(e) Identification of x-ray components. In addition to the
identification requirements specified in Sec. 1010.3 of this chapter,
manufacturers of components subject to this section and Sec. Sec.
1020.31, 1020.32, and 1020.33, except high-voltage generators contained
within tube housings and beam-limiting devices that are integral parts
of tube housings, shall permanently inscribe or affix thereon the model
number and serial number of the product so that they are legible and
accessible to view. The word ``model'' or ``type'' shall appear as part
of the manufacturer's required identification of certified x-ray
components. Where the certification of a system or subsystem,
consisting of two or more components, has been authorized under
paragraph (c) of this section, a single inscription, tag, or label
bearing the model number and serial number may be used to identify the
product.
(1) Tube housing assemblies. In a similar manner, manufacturers of
tube housing assemblies shall also inscribe or affix thereon the name
of the manufacturer, model number, and serial number of the x-ray tube
which the tube housing assembly incorporates.
(2) Replacement of tubes. Except as specified in paragraph (e)(3)
of this section, the replacement of an x-ray tube in a previously
manufactured tube housing assembly certified under paragraph (c) of
this section constitutes manufacture of a new tube housing assembly,
and the manufacturer is subject to the provisions of paragraph (e)(1)
of this section. The manufacturer shall remove, cover, or deface any
previously affixed inscriptions, tags, or labels, that are no longer
applicable.
(3) Quick-change x-ray tubes. The requirements of paragraph (e)(2)
of this section shall not apply to tube housing assemblies designed and
designated by their original manufacturer to contain quick change x-ray
tubes. The manufacturer of quick-change x-ray tubes shall include with
each replacement tube a label with the tube manufacturer's name, the
model, and serial number of the x-ray tube. The manufacturer of the
tube shall instruct the assembler who installs the new tube to attach
the label to the tube housing assembly and to remove, cover, or deface
the previously affixed inscriptions, tags, or labels that are described
by the tube manufacturer as no longer applicable.
(f) [Reserved]
(g) Information to be provided to assemblers. Manufacturers of
components listed in paragraph (a)(1) of this section shall provide to
assemblers subject to paragraph (d) of this section and, upon request,
to others at a cost not to exceed the cost of publication and
distribution, instructions for assembly, installation, adjustment, and
testing of such components adequate to assure that the products will
comply with applicable provisions of this section and Sec. Sec.
1020.31, 1020.32, and 1020.33, when assembled, installed, adjusted, and
tested as directed. Such instructions shall include specifications of
other components compatible with that to be installed when compliance
of the system or subsystem depends on their compatibility. Such
specifications may describe pertinent physical characteristics of the
components and/or may list by manufacturer model number the components
which are compatible. For x-ray controls and generators manufactured
after May 3, 1994, manufacturers shall provide:
(1) A statement of the rated line voltage and the range of line-
voltage regulation for operation at maximum line current;
(2) A statement of the maximum line current of the x-ray system
based on the maximum input voltage and current characteristics of the
tube housing assembly compatible with rated output voltage and rated
output current characteristics of the x-ray control and associated
high-voltage generator. If the rated input voltage and current
characteristics of the tube housing assembly are not known by the
manufacturer of the x-ray control and associated high-voltage
generator, the manufacturer shall provide information necessary to
allow the assembler to determine the maximum line current for the
particular tube housing assembly(ies);
(3) A statement of the technique factors that constitute the
maximum line current condition described in paragraph (g)(2) of this
section.
(h) Information to be provided to users. Manufacturers of x-ray
equipment shall provide to purchasers and, upon request, to others at a
cost not to exceed the cost of publication and distribution, manuals or
instruction sheets which shall include the following technical and
safety information:
(1) All x-ray equipment. For x-ray equipment to which this section
and Sec. Sec. 1020.31, 1020.32, and 1020.33 are applicable, there
shall be provided:
(i) Adequate instructions concerning any radiological safety
procedures and precautions which may be necessary because of unique
features of the equipment; and
(ii) A schedule of the maintenance necessary to keep the equipment
in compliance with this section and Sec. Sec. 1020.31, 1020.32, and
1020.33.
(2) Tube housing assemblies. For each tube housing assembly, there
shall be provided:
(i) Statements of the leakage technique factors for all
combinations of tube housing assemblies and beam-limiting devices for
which the tube housing assembly manufacturer states compatibility, the
minimum filtration permanently in the useful beam expressed as
millimeters of aluminum equivalent, and the peak tube potential at
which the aluminum equivalent was obtained;
(ii) Cooling curves for the anode and tube housing; and
(iii) Tube rating charts. If the tube is designed to operate from
different types of x-ray high-voltage generators (such as single-phase
self rectified, single-phase half-wave rectified, single-phase full-
wave rectified, 3-phase 6-pulse, 3-phase 12-pulse, constant potential,
capacitor energy storage) or under modes of operation such as alternate
focal spot sizes or speeds of anode rotation which affect its rating,
specific identification of the difference in ratings shall be noted.
(3) X-ray controls and generators. For the x-ray control and
associated x-ray high-voltage generator, there shall be provided:
(i) A statement of the rated line voltage and the range of line-
voltage regulation for operation at maximum line current;
(ii) A statement of the maximum line current of the x-ray system
based on the maximum input voltage and output current characteristics
of the tube housing assembly compatible with rated output voltage and
rated current characteristics of the x-ray control and associated high-
voltage generator. If the
[[Page 76086]]
rated input voltage and current characteristics of the tube housing
assembly are not known by the manufacturer of the x-ray control and
associated high-voltage generator, the manufacturer shall provide
necessary information to allow the purchaser to determine the maximum
line current for his particular tube housing assembly(ies);
(iii) A statement of the technique factors that constitute the
maximum line current condition described in paragraph (h)(3)(ii) of
this section;
(iv) In the case of battery-powered generators, a specification of
the minimum state of charge necessary for proper operation;
(v) Generator rating and duty cycle;
(vi) A statement of the maximum deviation from the preindication
given by labeled technique factor control settings or indicators during
any radiographic or CT exposure where the equipment is connected to a
power supply as described in accordance with this paragraph. In the
case of fixed technique factors, the maximum deviation from the nominal
fixed value of each factor shall be stated;
(vii) A statement of the maximum deviation from the continuous
indication of x-ray tube potential and current during any fluoroscopic
exposure when the equipment is connected to a power supply as described
in accordance with this paragraph; and
(viii) A statement describing the measurement criteria for all
technique factors used in paragraphs (h)(3)(iii), (h)(3)(vi), and
(h)(3)(vii) of this section; for example, the beginning and endpoints
of exposure time measured with respect to a certain percentage of the
voltage waveform.
(4) Beam-limiting device. For each variable-aperture beam-limiting
device, there shall be provided;
(i) Leakage technique factors for all combinations of tube housing
assemblies and beam-limiting devices for which the beam-limiting device
manufacturer states compatibility; and
(ii) A statement including the minimum aluminum equivalent of that
part of the device through which the useful beam passes and including
the x-ray tube potential at which the aluminum equivalent was obtained.
When two or more filters are provided as part of the device, the
statement shall include the aluminum equivalent of each filter.
(5) Imaging system information. For x-ray systems manufactured on
or after [date 1 year after date of publication of the final rule in
the Federal Register], that produce images using the fluoroscopic image
receptor, the following information shall be provided in a separate,
single section of the user's instruction manual or in a separate manual
devoted to this information:
(i) For each mode of operation, a description of the mode and
detailed instructions on how the mode is engaged and disengaged. This
information shall include how the operator can recognize which mode of
operation has been selected prior to initiation of x-ray production.
(ii) For each mode of operation, a description of any specific
clinical procedure(s) and clinical imaging task(s) for which the mode
is recommended or designed and how each mode should be used.
(6) Displays of values of AKR and cumulative air kerma. For
fluoroscopic x-ray systems manufactured on or after [date 1 year after
date of publication of the final rule in the Federal Register], the
following shall be provided:
(i) A statement of the maximum deviations of the AKR and cumulative
air kerma from their respective displayed values;
(ii) Instructions, including schedules, for calibrating and
maintaining any instrumentation associated with measurement or
evaluation of the AKR and cumulative air kerma;
(iii) Identification of the spatial coordinates of the irradiation
location to which displayed values of AKR and cumulative air kerma
refer according to Sec. 1020.32(k)(5);
(iv) A rationale for specification of a reference irradiation
location alternative to 15 centimeters from the isocenter toward the x-
ray source along the beam axis when such alternative specification is
made according to Sec. 1020.32(k)(5)(ii).
(i) [Reserved]
(j) Warning label. The control panel containing the main power
switch shall bear the warning statement, legible and accessible to
view:
``Warning: This x-ray unit may be dangerous to patient and
operator unless safe exposure factors, operating instructions and
maintenance schedules are observed.''
(k) Leakage radiation from the diagnostic source assembly. The
leakage radiation from the diagnostic source assembly measured at a
distance of 1 meter in any direction from the source shall not exceed
0.88 milligray (mGy) air kerma (vice 100 milliroentgen (mR) exposure)
in 1 hour when the x-ray tube is operated at the leakage technique
factors. If the maximum rated peak tube potential of the tube housing
assembly is greater than the maximum rated peak tube potential for the
diagnostic source assembly, positive means shall be provided to limit
the maximum x-ray tube potential to that of the diagnostic source
assembly. Compliance shall be determined by measurements averaged over
an area of 100 square centimeters with no linear dimension greater than
20 centimeters.
(l) Radiation from components other than the diagnostic source
assembly. The radiation emitted by a component other than the
diagnostic source assembly shall not exceed an air kerma of 18 microGy
(vice 2 mR exposure) in 1 hour at 5 centimeters from any accessible
surface of the component when it is operated in an assembled x-ray
system under any conditions for which it was designed. Compliance shall
be determined by measurements averaged over an area of 100 square
centimeters with no linear dimension greater than 20 centimeters.
(m) Beam quality--(1) Half-value layer. The half-value layer (HVL)
of the useful beam for a given x-ray tube potential shall not be less
than the appropriate value shown in table 1 of this section under
``Specified Dental Systems,'' for any dental x-ray system designed for
use with intraoral image receptors and manufactured after December 1,
1980; under ``I--Other X-Ray Systems,'' for any dental x-ray system
designed for use with intraoral image receptors and manufactured before
December 1, 1980, and all other x-ray systems subject to this section
and manufactured before [date 1 year after date of publication of the
final rule in the Federal Register]; and under ``II--Other X-Ray
Systems,'' for all x-ray systems, except dental x-ray systems designed
for use with intraoral image receptors, subject to this section and
manufactured on or after [date 1 year after date of publication of the
final rule in the Federal Register]. If it is necessary to determine
such HVL at an x-ray tube potential which is not listed in table 1 of
this section, linear interpolation or extrapolation may be made.
Positive means\2\ shall be provided to insure that at least the minimum
filtration needed to achieve the above beam quality requirements is in
the useful beam during each exposure. Table 1 follows:
---------------------------------------------------------------------------
\2\In the case of a system which is to be operated with more
than one thickness of filtration, this requirement can be met by a
filter interlocked with the kilovoltage selector which will prevent
x-ray emissions if the minimum required filtration is not in place.
[[Page 76087]]
Table 1.
--------------------------------------------------------------------------------------------------------------------------------------------------------
X-Ray Tube Voltage (kilovolt peak) Minimum HVL (millimeters of aluminum)
--------------------------------------------------------------------------------------------------------------------------------------------------------
Measured Operating Specified Dental I--Other X-Ray II--Other X-Ray
Designed Operating Range Potential Systems\1\ Systems\2\ Systems\3\
--------------------------------------------------------------------------------------------------------------------------------------------------------
Below 51 30 1.5 0.3 0.3
--------------------------------------------------------------------------------------------------------------------------------------------------------
40 1.5 0.4 0.4
--------------------------------------------------------------------------------------------------------------------------------------------------------
50 1.5 0.5 0.5
--------------------------------------------------------------------------------------------------------------------------------------------------------
51 to 70 51 1.5 1.2 1.3
--------------------------------------------------------------------------------------------------------------------------------------------------------
60 1.5 1.3 1.5
--------------------------------------------------------------------------------------------------------------------------------------------------------
70 1.5 1.5 1.8
--------------------------------------------------------------------------------------------------------------------------------------------------------
Above 70 71 2.1 2.1 2.4
--------------------------------------------------------------------------------------------------------------------------------------------------------
80 2.3 2.3 2.8
--------------------------------------------------------------------------------------------------------------------------------------------------------
90 2.5 2.5 3.2
--------------------------------------------------------------------------------------------------------------------------------------------------------
100 2.7 2.7 3.6
--------------------------------------------------------------------------------------------------------------------------------------------------------
110 3.0 3.0 4.1
--------------------------------------------------------------------------------------------------------------------------------------------------------
120 3.2 3.2 4.5
--------------------------------------------------------------------------------------------------------------------------------------------------------
130 3.5 3.5 5.0
--------------------------------------------------------------------------------------------------------------------------------------------------------
140 3.8 3.8 5.4
--------------------------------------------------------------------------------------------------------------------------------------------------------
150 4.1 4.1 5.9
--------------------------------------------------------------------------------------------------------------------------------------------------------
\1\Dental x-ray systems designed for use with intraoral image receptors and manufactured after December 1, 1980.
\2\Dental x-ray systems designed for use with intraoral image receptors and manufactured before or on December 1, 1980, and all other x-ray systems
subject to this section and manufactured before or on [date 1 year after date of publication of the final rule in the Federal Register].
\3\All x-ray systems, except dental x-ray systems designed for use with intraoral image receptors, subject to this section and manufactured after [date
1 year after date of publication of the final rule in the Federal Register].
(2) Optional filtration. Fluoroscopic systems incorporating an x-
ray tube(s) with a continuous output of 1 kilowatt or more and an anode
heat storage capacity of 1 million heat units or more shall provide the
option of selecting and adding x-ray filtration to the diagnostic
source assembly over and above the amount needed to meet the half-value
layer provisions of Sec. 1020.30(m)(1). The selection of this
additional x-ray filtration shall be at the option of the user.
(3) Measuring compliance. For capacitor energy storage equipment,
compliance shall be determined with the maximum selectable quantity of
charge per exposure.
(n) Aluminum equivalent of material between patient and image
receptor. Except when used in a CT x-ray system, the aluminum
equivalent of each of the items listed in table 2 of this section,
which are used between the patient and image receptor, may not exceed
the indicated limits. Compliance shall be determined by x-ray
measurements made at a potential of 100 kilovolts peak and with an x-
ray beam that has a HVL specified in table 1 of this section for the
potential. This requirement applies to front panel(s) of cassette
holders and film changers provided by the manufacturer for patient
support or for prevention of foreign object intrusions. It does not
apply to screens and their associated mechanical support panels or
grids. Table 2 follows:
Table 2.
------------------------------------------------------------------------
Aluminum
Item Equivalent
(millimeters)
------------------------------------------------------------------------
Front panel(s) of cassette holders (total of all) 1.0
Front panel(s) of film changer (total of all) 1.0
Cradle 2.0
Tabletop, stationary, without articulated joints 1.0
Tabletop, movable, without articulated joint(s) 1.5
(including stationary subtop)
Tabletop, with radiolucent panel having one 1.5
articulated joint
Tabletop, with radiolucent panel having two or more 2.0
articulated joints
Tabletop, cantilevered 2.0
Tabletop, radiation therapy simulator 5.0
------------------------------------------------------------------------
[[Page 76088]]
(o) Battery charge indicator. On battery-powered generators, visual
means shall be provided on the control panel to indicate whether the
battery is in a state of charge adequate for proper operation.
(p) [Reserved]
(q) Modification of certified diagnostic x-ray components and
systems--(1) Diagnostic x-ray components and systems certified in
accordance with Sec. 1010.2 of this chapter shall not be modified such
that the component or system fails to comply with any applicable
provision of this chapter unless a variance in accordance with Sec.
1010.4 of this chapter or an exemption under section 534(a)(5) or
538(b) of the Federal Food, Drug, and Cosmetic Act has been granted.
(2) The owner of a diagnostic x-ray system who uses the system in a
professional or commercial capacity may modify the system, provided the
modification does not result in the failure of the system or component
to comply with the applicable requirements of this section or of Sec.
1020.31, Sec. 1020.32, or Sec. 1020.33. The owner who causes such
modification need not submit the reports required by subpart B of part
1002 of this chapter, provided the owner records the date and the
details of the modification, and provided the modification of the x-ray
system does not result in a failure to comply with Sec. 1020.31, Sec.
1020.32, or Sec. 1020.33.
3. Revise Sec. 1020.31 to read as follows:
Sec. 1020.31 Radiographic equipment.
The provisions of this section apply to equipment for the recording
of images, except equipment for fluoroscopic imaging and for
radiographic imaging when images are recorded from the fluoroscopic
image receptor or computed tomography x-ray systems manufactured on or
after November 28, 1984.
(a) Control and indication of technique factors--(1) Visual
indication. The technique factors to be used during an exposure shall
be indicated before the exposure begins, except when automatic exposure
controls are used, in which case the technique factors which are set
prior to the exposure shall be indicated. On equipment having fixed
technique factors, this requirement may be met by permanent markings.
Indication of technique factors shall be visible from the operator's
position except in the case of spot films made by the fluoroscopist.
(2) Timers. Means shall be provided to terminate the exposure at a
preset time interval, a preset product of current and time, a preset
number of pulses, or a preset radiation exposure to the image receptor.
(i) Except during serial radiography, the operator shall be able to
terminate the exposure at any time during an exposure of greater than
one-half second. Except during panoramic dental radiography,
termination of exposure shall cause automatic resetting of the timer to
its initial setting or to zero. It shall not be possible to make an
exposure when the timer is set to a zero or off position if either
position is provided.
(ii) During serial radiography, the operator shall be able to
terminate the x-ray exposure(s) at any time, but means may be provided
to permit completion of any single exposure of the series in process.
(3) Automatic exposure controls. When an automatic exposure control
is provided:
(i) Indication shall be made on the control panel when this mode of
operation is selected;
(ii) When the x-ray tube potential is equal to or greater than 51
kilovolts peak (kVp), the minimum exposure time for field emission
equipment rated for pulsed operation shall be equal to or less than a
time interval equivalent to two pulses and the minimum exposure time
for all other equipment shall be equal to or less than 1/60 second or a
time interval required to deliver 5 milliampere-seconds (mAs),
whichever is greater;
(iii) Either the product of peak x-ray tube potential, current, and
exposure time shall be limited to not more than 60 kilowatt-seconds
(kWs) per exposure or the product of x-ray tube current and exposure
time shall be limited to not more than 600 mAs per exposure, except
when the x-ray tube potential is less than 51 kVp, in which case the
product of x-ray tube current and exposure time shall be limited to not
more than 2,000 mAs per exposure; and
(iv) A visible signal shall indicate when an exposure has been
terminated at the limits described in paragraph (a)(3)(iii) of this
section, and manual resetting shall be required before further
automatically timed exposures can be made.
(4) Accuracy. Deviation of technique factors from indicated values
shall not exceed the limits given in the information provided in
accordance with Sec. 1020.30(h)(3);
(b) Reproducibility. The following requirements shall apply when
the equipment is operated on an adequate power supply as specified by
the manufacturer in accordance with the requirements of Sec.
1020.30(h)(3);
(1) Coefficient of variation. For any specific combination of
selected technique factors, the estimated coefficient of variation of
the air kerma shall be no greater than 0.05.
(2) Measuring compliance. Determination of compliance shall be
based on 10 consecutive measurements taken within a time period of 1
hour. Equipment manufactured after September 5, 1978, shall be subject
to the additional requirement that all variable controls for technique
factors shall be adjusted to alternate settings and reset to the test
setting after each measurement. The percent line-voltage regulation
shall be determined for each measurement. All values for percent line-
voltage regulation shall be within +/-1 of the mean value for all
measurements. For equipment having automatic exposure controls,
compliance shall be determined with a sufficient thickness of
attenuating material in the useful beam such that the technique factors
can be adjusted to provide individual exposures of a minimum of 12
pulses on field emission equipment rated for pulsed operation or no
less than one-tenth second per exposure on all other equipment.
(c) Linearity. The following requirements apply when the equipment
is operated on a power supply as specified by the manufacturer in
accordance with the requirements of Sec. 1020.30(h)(3) for any fixed
x-ray tube potential within the range of 40 percent to 100 percent of
the maximum rated.
(1) Equipment having independent selection of x-ray tube current
(mA). The average ratios of air kerma to the indicated milliampere-
seconds product (mGy/mAs) obtained at any two consecutive tube current
settings shall not differ by more than 0.10 times their sum. This is:
|X1 - X2|<=0.10(X1+X2);
where X1 and X2 are the average mGy/mAs values
obtained at each of two consecutive tube current settings or at two
settings differing by no more than a factor of 2 where the tube current
selection is continuous.
(2) Equipment having selection of x-ray tube current-exposure time
product (mAs). For equipment manufactured after May 3, 1994, the
average ratios of air kerma to the indicated milliampere-seconds
product (mGy/mAs) obtained at any two consecutive mAs selector settings
shall not differ by more than 0.10 times their sum. This is:
|X1-X2|<= 0.10(X1+X2);
where X1 and X2 are the average mGy/mAs values
obtained at each of two consecutive mAs selector settings or at two
settings differing by no more than a factor of 2 where the mAs selector
provides continuous selection.
[[Page 76089]]
(3) Measuring compliance. Determination of compliance will be based
on 10 exposures, made within 1 hour, at each of the two settings. These
two settings may include any two focal spot sizes except where one is
equal to or less than 0.45 millimeters and the other is greater than
0.45 millimeters. For purposes of this requirement, focal spot size is
the focal spot size specified by the x-ray tube manufacturer. The
percent line-voltage regulation shall be determined for each
measurement. All values for percent line-voltage regulation at any one
combination of technique factors shall be within +/-1 of the mean value
for all measurements at these technique factors.
(d) Field limitation and alignment for mobile, portable, and
stationary general purpose x-ray systems. Except when spot-film devices
are in service, mobile, portable, and stationary general purpose
radiographic x-ray systems shall meet the following requirements:
(1) Variable x-ray field limitation. A means for stepless
adjustment of the size of the x-ray field shall be provided. Each
dimension of the minimum field size at an SID of 100 centimeters shall
be equal to or less than 5 centimeters.
(2) Visual definition. (i) Means for visually defining the
perimeter of the x-ray field shall be provided. The total misalignment
of the edges of the visually defined field with the respective edges of
the x-ray field along either the length or width of the visually
defined field shall not exceed 2 percent of the distance from the
source to the center of the visually defined field when the surface
upon which it appears is perpendicular to the axis of the x-ray beam.
(ii) When a light localizer is used to define the x-ray field, it
shall provide an average illuminance of not less than 160 lux (15
footcandles) at 100 centimeters or at the maximum SID, whichever is
less. The average illuminance shall be based upon measurements made in
the approximate center of each quadrant of the light field. Radiation
therapy simulation systems are exempt from this requirement.
(iii) The edge of the light field at 100 centimeters or at the
maximum SID, whichever is less, shall have a contrast ratio, corrected
for ambient lighting, of not less than 4 in the case of beam-limiting
devices designed for use on stationary equipment, and a contrast ratio
of not less than 3 in the case of beam-limiting devices designed for
use on mobile and portable equipment. The contrast ratio is defined as
I1/I2, where I1 is the illuminance 3
millimeters from the edge of the light field toward the center of the
field; and I2 is the illuminance 3 millimeters from the edge
of the light field away from the center of the field. Compliance shall
be determined with a measuring aperture of 1 millimeter.
(e) Field indication and alignment on stationary general purpose x-
ray equipment. Except when spot-film devices are in service, stationary
general purpose x-ray systems shall meet the following requirements in
addition to those prescribed in paragraph (d) of this section:
(1) Means shall be provided to indicate when the axis of the x-ray
beam is perpendicular to the plane of the image receptor, to align the
center of the x-ray field with respect to the center of the image
receptor to within 2 percent of the SID, and to indicate the SID to
within 2 percent;
(2) The beam-limiting device shall numerically indicate the field
size in the plane of the image receptor to which it is adjusted;
(3) Indication of field size dimensions and SIDs shall be specified
in centimeters and/or inches and shall be such that aperture
adjustments result in x-ray field dimensions in the plane of the image
receptor which correspond to those indicated by the beam-limiting
device to within 2 percent of the SID when the beam axis is indicated
to be perpendicular to the plane of the image receptor; and
(4) Compliance measurements will be made at discrete SIDs and image
receptor dimensions in common clinical use (such as SIDs of 100, 150,
and 200 centimeters and/or 36, 40, 48, and 72 inches and nominal image
receptor dimensions of 13, 18, 24, 30, 35, 40, and 43 centimeters and/
or 5, 7, 8, 9, 10, 11, 12, 14, and 17 inches) or at any other specific
dimensions at which the beam-limiting device or its associated
diagnostic x-ray system is uniquely designed to operate.
(f) Field limitation on radiographic x-ray equipment other than
general purpose radiographic systems--(1) Equipment for use with
intraoral image receptors. Radiographic equipment designed for use with
an intraoral image receptor shall be provided with means to limit the
x-ray beam such that:
(i) If the minimum source-to-skin distance (SSD) is 18 centimeters
or more, the x-ray field at the minimum SSD shall be containable in a
circle having a diameter of no more than 7 centimeters; and
(ii) If the minimum SSD is less than 18 centimeters, the x-ray
field at the minimum SSD shall be containable in a circle having a
diameter of no more than 6 centimeters.
(2) X-ray systems designed for one image receptor size.
Radiographic equipment designed for only one image receptor size at a
fixed SID shall be provided with means to limit the field at the plane
of the image receptor to dimensions no greater than those of the image
receptor, and to align the center of the x-ray field with the center of
the image receptor to within 2 percent of the SID or shall be provided
with means to both size and align the x-ray field such that the x-ray
field at the plane of the image receptor does not extend beyond any
edge of the image receptor.
(3) Systems designed for mammography--(i) Radiographic systems
designed only for mammography and general purpose radiography systems,
when special attachments for mammography are in service, manufactured
on or after November 1, 1977, and before September 30, 1999, shall be
provided with means to limit the useful beam such that the x-ray field
at the plane of the image receptor does not extend beyond any edge of
the image receptor at any designated SID except the edge of the image
receptor designed to be adjacent to the chest wall where the x-ray
field may not extend beyond this edge by more than 2 percent of the
SID. This requirement can be met with a system that performs as
prescribed in paragraphs (f)(4)(i), (f)(4)(ii), and (f)(4)(iii) of this
section. When the beam-limiting device and image receptor support
device are designed to be used to immobilize the breast during a
mammographic procedure and the SID may vary, the SID indication
specified in paragraphs (f)(4)(ii) and (f)(4)(iii) of this section
shall be the maximum SID for which the beam-limiting device or aperture
is designed.
(ii) Mammographic beam-limiting devices manufactured on or after
September 30, 1999, shall be provided with the means to limit the
useful beam such that the x-ray field at the plane of the image
receptor does not extend beyond any edge of the image receptor by more
than 2 percent of the SID. This requirement can be met with a system
that performs as prescribed in paragraphs (f)(4)(i), (f)(4)(ii), and
(f)(4)(iii) of this section. For systems that allow changes in the SID,
the SID indication specified in paragraphs (f)(4)(ii) and (f)(4)(iii)
of this section shall be the maximum SID for which the beam-limiting
device or aperture is designed.
(iii) Each image receptor support device manufactured on or after
November 1, 1977, intended for installation on a system designed for
mammography shall have clear and
[[Page 76090]]
permanent markings to indicate the maximum image receptor size for
which it is designed.
(4) Other x-ray systems. Radiographic systems not specifically
covered in paragraphs (d), (e), (f)(2), (f)(3), and (h) of this section
and systems covered in paragraph (f)(1) of this section, which are also
designed for use with extraoral image receptors and when used with an
extraoral image receptor, shall be provided with means to limit the x-
ray field in the plane of the image receptor so that such field does
not exceed each dimension of the image receptor by more than 2 percent
of the SID, when the axis of the x-ray beam is perpendicular to the
plane of the image receptor. In addition, means shall be provided to
align the center of the x-ray field with the center of the image
receptor to within 2 percent of the SID, or means shall be provided to
both size and align the x-ray field such that the x-ray field at the
plane of the image receptor does not extend beyond any edge of the
image receptor. These requirements may be met with:
(i) A system which performs in accordance with paragraphs (d) and
(e) of this section; or when alignment means are also provided, may be
met with either;
(ii) An assortment of removable, fixed-aperture, beam-limiting
devices sufficient to meet the requirement for each combination of
image receptor size and SID for which the unit is designed. Each such
device shall have clear and permanent markings to indicate the image
receptor size and SID for which it is designed; or
(iii) A beam-limiting device having multiple fixed apertures
sufficient to meet the requirement for each combination of image
receptor size and SID for which the unit is designed. Permanent,
clearly legible markings shall indicate the image receptor size and SID
for which each aperture is designed and shall indicate which aperture
is in position for use.
(g) Positive beam limitation (PBL). The requirements of this
paragraph shall apply to radiographic systems which contain PBL.
(1) Field size. When a PBL system is provided, it shall prevent x-
ray production when:
(i) Either the length or width of the x-ray field in the plane of
the image receptor differs from the corresponding image receptor
dimension by more than 3 percent of the SID; or
(ii) The sum of the length and width differences as stated in
paragraph (g)(1)(i) of this section without regard to sign exceeds 4
percent of the SID.
(iii) The beam limiting device is at an SID for which PBL is not
designed for sizing.
(2) Conditions for PBL. When provided, the PBL system shall
function as described in paragraph (g)(1) of this section whenever all
the following conditions are met:
(i) The image receptor is inserted into a permanently mounted
cassette holder;
(ii) The image receptor length and width are less than 50
centimeters;
(iii) The x-ray beam axis is within +/-3 degrees of vertical and
the SID is 90 centimeters to 130 centimeters inclusive; or the x-ray
beam axis is within +/-3 degrees of horizontal and the SID is 90
centimeters to 205 centimeters inclusive;
(iv) The x-ray beam axis is perpendicular to the plane of the image
receptor to within +/-3 degrees; and
(v) Neither tomographic nor stereoscopic radiography is being
performed.
(3) Measuring compliance. Compliance with the requirements of
paragraph (g)(1) of this section shall be determined when the equipment
indicates that the beam axis is perpendicular to the plane of the image
receptor and the provisions of paragraph (g)(2) of this section are
met. Compliance shall be determined no sooner than 5 seconds after
insertion of the image receptor.
(4) Operator initiated undersizing. The PBL system shall be capable
of operation such that, at the discretion of the operator, the size of
the field may be made smaller than the size of the image receptor
through stepless adjustment of the field size. Each dimension of the
minimum field size at an SID of 100 centimeters shall be equal to or
less than 5 centimeters. Return to PBL function as described in
paragraph (g)(1) of this section shall occur automatically upon any
change of image receptor size or SID.
(5) Override of PBL. A capability may be provided for overriding
PBL in case of system failure and for servicing the system. This
override may be for all SIDs and image receptor sizes. A key shall be
required for any override capability that is accessible to the
operator. It shall not be possible to remove the key while PBL is
overridden. Each such key switch or key shall be clearly and durably
labeled as follows:
For X-ray Field Limitation System Failure
The override capability is considered accessible to the operator
if it is referenced in the operator's manual or in other material
intended for the operator or if its location is such that the
operator would consider it part of the operational controls.
(h) Field limitation and alignment for spot-film devices. The
following requirements shall apply to spot-film devices, except when
the spot-film device is provided for use with a radiation therapy
simulation system:
(1) Means shall be provided between the source and the patient for
adjustment of the x-ray field size in the plane of the image receptor
to the size of that portion of the image receptor which has been
selected on the spot-film selector. Such adjustment shall be
accomplished automatically when the x-ray field size in the plane of
the image receptor is greater than the selected portion of the image
receptor. If the x-ray field size is less than the size of the selected
portion of the image receptor, the field size shall not open
automatically to the size of the selected portion of the image receptor
unless the operator has selected that mode of operation.
(2) Neither the length nor the width of the x-ray field in the
plane of the image receptor shall differ from the corresponding
dimensions of the selected portion of the image receptor by more than 3
percent of the SID when adjusted for full coverage of the selected
portion of the image receptor. The sum, without regard to sign, of the
length and width differences shall not exceed 4 percent of the SID. On
spot-film devices manufactured after February 25, 1978, if the angle
between the plane of the image receptor and beam axis is variable,
means shall be provided to indicate when the axis of the x-ray beam is
perpendicular to the plane of the image receptor, and compliance shall
be determined with the beam axis indicated to be perpendicular to the
plane of the image receptor.
(3) The center of the x-ray field in the plane of the image
receptor shall be aligned with the center of the selected portion of
the image receptor to within 2 percent of the SID.
(4) Means shall be provided to reduce the x-ray field size in the
plane of the image receptor to a size smaller than the selected portion
of the image receptor such that:
(i) For spot-film devices used on fixed-SID fluoroscopic systems
which are not required to, and do not provide stepless adjustment of
the x-ray field, the minimum field size, at the greatest SID, does not
exceed 125 square centimeters; or
(ii) For spot-film devices used on fluoroscopic systems that have a
variable SID and/or stepless adjustment of the field size, the minimum
field size, at the greatest SID, shall be containable in a square of 5
centimeters by 5 centimeters.
[[Page 76091]]
(5) A capability may be provided for overriding the automatic x-ray
field size adjustment in case of system failure. If it is so provided,
a signal visible at the fluoroscopist's position shall indicate
whenever the automatic x-ray field size adjustment override is engaged.
Each such system failure override switch shall be clearly labeled as
follows:
For X-ray Field Limitation System Failure
(i) Source-skin distance--(1) X-ray systems designed for use with
an intraoral image receptor shall be provided with means to limit the
source-skin distance to not less than:
(i) Eighteen centimeters if operable above 50 kVp; or
(ii) Ten centimeters if not operable above 50 kVp.
(2) Mobile and portable x-ray systems other than dental shall be
provided with means to limit the source-skin distance to not less than
30 centimeters.
(j) Beam-on indicators. The x-ray control shall provide visual
indication whenever x-rays are produced. In addition, a signal audible
to the operator shall indicate that the exposure has terminated.
(k) Multiple tubes. Where two or more radiographic tubes are
controlled by one exposure switch, the tube or tubes which have been
selected shall be clearly indicated before initiation of the exposure.
This indication shall be both on the x-ray control and at or near the
tube housing assembly which has been selected.
(l) Radiation from capacitor energy storage equipment. Radiation
emitted from the x-ray tube shall not exceed:
(1) An air kerma of 0.26 mGy (vice 0.03 mR exposure) in 1 minute at
5 centimeters from any accessible surface of the diagnostic source
assembly, with the beam-limiting device fully open, the system fully
charged, and the exposure switch, timer, or any discharge mechanism not
activated. Compliance shall be determined by measurements averaged over
an area of 100 square centimeters, with no linear dimension greater
than 20 centimeters; and
(2) An air kerma of 0.88 mGy (vice 100 mR exposure) in 1 hour at
100 centimeters from the x-ray source, with the beam-limiting device
fully open, when the system is discharged through the x-ray tube either
manually or automatically by use of a discharge switch or deactivation
of the input power. Compliance shall be determined by measurements of
the maximum air kerma per discharge multiplied by the total number of
discharges in 1 hour (duty cycle). The measurements shall be averaged
over an area of 100 square centimeters with no linear dimension greater
than 20 centimeters.
(m) Primary protective barrier for mammography x-ray systems--(1)
For x-ray systems manufactured after September 5, 1978, and before
September 30, 1999, which are designed only for mammography, the
transmission of the primary beam through any image receptor support
provided with the system shall be limited such that the air kerma 5
centimeters from any accessible surface beyond the plane of the image
receptor supporting device does not exceed 0.88 microGy (vice 0.1 mR
exposure) for each activation of the tube.
(2) For mammographic x-ray systems manufactured on or after
September 30, 1999:
(i) At any SID where exposures can be made, the image receptor
support device shall provide a primary protective barrier that
intercepts the cross section of the useful beam along every direction
except at the chest wall edge.
(ii) The x-ray system shall not permit exposure unless the
appropriate barrier is in place to intercept the useful beam as
required in paragraph (m)(2)(i) of this section.
(iii) The transmission of the useful beam through the primary
protective barrier shall be limited such that the air kerma 5
centimeters from any accessible surface beyond the plane of the primary
protective barrier does not exceed 0.88 microGy (vice 0.1 mR exposure)
for each activation of the tube.
(3) Compliance with the requirements of paragraphs (m)(1) and
(m)(2)(iii) of this section for transmission shall be determined with
the x-ray system operated at the minimum SID for which it is designed,
at the maximum rated peak tube potential, at the maximum rated product
of x-ray tube current and exposure time (mAs) for the maximum rated
peak tube potential, and by measurements averaged over an area of 100
square centimeters with no linear dimension greater than 20
centimeters. The sensitive volume of the radiation measuring instrument
shall not be positioned beyond the edge of the primary protective
barrier along the chest wall side.
4. Revise Sec. 1020.32 to read as follows:
Sec. 1020.32 Fluoroscopic equipment.
The provisions of this section apply to equipment for fluoroscopic
imaging and for radiographic imaging when images are recorded from the
fluoroscopic image receptor except computed tomography x-ray systems
manufactured on or after November 29, 1984.
(a) Primary protective barrier--(1) Limitation of useful beam. The
fluoroscopic imaging assembly shall be provided with a primary
protective barrier which intercepts the entire cross section of the
useful beam at any SID. The x-ray tube used for fluoroscopy shall not
produce x-rays unless the barrier is in position to intercept the
entire useful beam. The AKR due to transmission through the barrier
with the attenuation block in the useful beam combined with radiation
from the fluoroscopic image receptor shall not exceed 3.34 x
10-3 percent of the entrance AKR, at a distance of 10
centimeters from any accessible surface of the fluoroscopic imaging
assembly beyond the plane of the image receptor. Radiation therapy
simulation systems shall be exempt from this requirement provided the
systems are intended only for remote control operation and the
manufacturer sets forth instructions for assemblers with respect to
control location as part of the information required in Sec.
1020.30(g). Additionally, the manufacturer shall provide to users,
under Sec. 1020.30(h)(1)(i), precautions concerning the importance of
remote control operation.
(2) Measuring compliance. The AKR shall be measured in accordance
with paragraph (d) of this section. The AKR due to transmission through
the primary barrier combined with radiation from the fluoroscopic image
receptor shall be determined by measurements averaged over an area of
100 square centimeters with no linear dimension greater than 20
centimeters. If the source is below the tabletop, the measurement shall
be made with the input surface of the fluoroscopic imaging assembly
positioned 30 centimeters above the tabletop. If the source is above
the tabletop and the SID is variable, the measurement shall be made
with the end of the beam-limiting device or spacer as close to the
tabletop as it can be placed, provided that it shall not be closer than
30 centimeters. Movable grids and compression devices shall be removed
from the useful beam during the measurement. For all measurements, the
attenuation block shall be positioned in the useful beam 10 centimeters
from the point of measurement of entrance AKR and between this point
and the input surface of the fluoroscopic imaging assembly.
(b) Field limitation--(1) Angulation. For fluoroscopic equipment
manufactured after February 25, 1978, when the angle between the image
receptor and the beam axis of the x-ray beam is variable, means shall
be provided to indicate when the axis of the x-ray beam is
perpendicular to the plane of the image receptor. Compliance with
paragraphs (b)(4) and (b)(5) of this section shall be determined with
the
[[Page 76092]]
beam axis indicated to be perpendicular to the plane of the image
receptor.
(2) Further means for limitation. Means shall be provided to permit
further limitation of the x-ray field to sizes smaller than the limits
of paragraphs (b)(4) and (b)(5). Beam-limiting devices manufactured
after May 22, 1979, and incorporated in equipment with a variable SID
and/or the capability of a visible area of greater than 300 square
centimeters shall be provided with means for stepless adjustment of the
x-ray field. Equipment with a fixed SID and the capability of a visible
area of no greater than 300 square centimeters shall be provided with
either stepless adjustment of the x-ray field or with a means to
further limit the x-ray field size at the plane of the image receptor
to 125 square centimeters or less. Stepless adjustment shall, at the
greatest SID, provide continuous field sizes from the maximum
obtainable to a field size containable in a square of 5 centimeters by
5 centimeters. This paragraph does not apply to nonimage-intensified
fluoroscopy.
(3) Nonimage-intensified fluoroscopy. The x-ray field produced by
nonimage-intensified fluoroscopic equipment shall not extend beyond the
entire visible area of the image receptor. Means shall be provided for
stepless adjustment of field size. The minimum field size, at the
greatest SID, shall be containable in a square of 5 centimeters by 5
centimeters.
(4) Fluoroscopy and radiography using the fluoroscopic imaging
assembly with inherently circular image receptors. (i) For fluoroscopic
equipment manufactured before [date 1 year after date of publication of
the final rule in the Federal Register], other than radiation therapy
simulation systems, the following applies:
(A) Neither the length nor the width of the x-ray field in the
plane of the image receptor shall exceed that of the visible area of
the image receptor by more than 3 percent of the SID. The sum of the
excess length and the excess width shall be no greater than 4 percent
of the SID.
(B) For rectangular x-ray fields used with circular image
receptors, the error in alignment shall be determined along the length
and width dimensions of the x-ray field which pass through the center
of the visible area of the image receptor.
(ii) For fluoroscopic equipment manufactured on or after [date 1
year after date of publication of the final rule in the Federal
Register], other than radiation therapy simulation systems, the maximum
area of the x-ray field in the plane of the image receptor shall
conform with one of the following requirements:
(A) When the visible area of the image receptor is less than or
equal to 34 cm in any direction: (1) At least 80 percent of the x-ray
field overlaps the visible area of the image receptor, or (2) at least
80 percent of the air kerma integrated over the x-ray field is incident
on the area of the image receptor.
(B) When the visible area of the image receptor is greater than 34
cm in any direction, the x-ray field measured along the direction of
greatest misalignment with the visible area of the image receptor shall
not extend beyond the visible area of the image receptor by more than a
total of 2 cm.
(5) Fluoroscopy and radiography using the fluoroscopic imaging
assembly with inherently rectangular image receptors. For x-ray systems
manufactured after [date 1 year after date of publication of the final
rule in the Federal Register]:
(i) Neither the length nor the width of the x-ray field in the
plane of the image receptor shall exceed that of the visible area of
the image receptor by more than 3 percent of the SID. The sum of the
excess length and the excess width shall be no greater than 4 percent
of the SID.
(ii) The error in alignment shall be determined along the length
and width dimensions of the x-ray field which pass through the center
of the visible area of the image receptor.
(6) Override capability. If the fluoroscopic x-ray field size is
adjusted automatically as the SID or image receptor size is changed, a
capability may be provided for overriding the automatic adjustment in
case of system failure. If it is so provided, a signal visible at the
fluoroscopist's position shall indicate whenever the automatic field
adjustment is overridden. Each such system failure override switch
shall be clearly labeled as follows:
For X-ray Field Limitation System Failure
(c) Activation of tube. X-ray production in the fluoroscopic mode
shall be controlled by a device which requires continuous pressure by
the operator for the entire time of any exposure. When recording serial
fluoroscopic images, the operator shall be able to terminate the x-ray
exposure(s) at any time, but means may be provided to permit completion
of any single exposure of the series in process.
(d) Air kerma rates. For fluoroscopic equipment, the following
requirements apply:
(1) Fluoroscopic equipment manufactured before May 19, 1995-- (i)
Equipment provided with automatic exposure rate control (AERC) shall
not be operable at any combination of tube potential and current that
will result in an AKR in excess of 88 mGy per minute (vice 10 R/min
exposure rate) at the measurement point specified in Sec.
1020.32(d)(3), except as specified in Sec. 1020.32(d)(1)(v) of this
section.
(ii) Equipment provided without AERC shall not be operable at any
combination of tube potential and current that will result in an AKR in
excess of 44 mGy per minute (vice 5 R/min exposure rate) at the
measurement point specified in Sec. 1020.32(d)(3), except as specified
in Sec. 1020.32(d)(1)(v) of this section.
(iii) Equipment provided with both an AERC mode and a manual mode
shall not be operable at any combination of tube potential and current
that will result in an AKR in excess of 88 mGy per minute (vice 10 R/
min exposure rate) in either mode at the measurement point specified in
Sec. 1020.32(d)(3), except as specified in Sec. 1020.32(d)(1)(v) of
this section.
(iv) Equipment may be modified in accordance with Sec. 1020.30(q)
to comply with Sec. 1020.32(d)(2). When the equipment is modified, it
shall bear a label indicating the date of the modification and the
statement:
``Modified to comply with 21 CFR 1020.32(d)(2).''
(v) Exceptions:
(A) During recording of fluoroscopic images, or
(B) When a mode of operation has an optional high-level control, in
which case that mode shall not be operable at any combination of tube
potential and current that will result in an AKR in excess of the rates
specified in Sec. 1020.32(d)(1)(i), (d)(1)(ii), or (d)(1)(iii) at the
measurement point specified in Sec. 1020.32(d)(3), unless the high-
level control is activated. Special means of activation of high-level
controls shall be required. The high-level control shall be operable
only when continuous manual activation is provided by the operator. A
continuous signal audible to the fluoroscopist shall indicate that the
high-level control is being employed.
(2) Fluoroscopic equipment manufactured on or after May 19, 1995--
(i) Shall be equipped with AERC if operable at any combination of tube
potential and current that results in an AKR greater than 44 mGy per
minute (vice 5 R/min exposure rate) at the measurement point specified
in Sec. 1020.32(d)(3). Provision for manual selection of technique
factors may be provided.
(ii) Shall not be operable at any combination of tube potential and
current that will result in an AKR in excess of 88 mGy per minute (vice
10
[[Page 76093]]
R/min exposure rate) at the measurement point specified in Sec.
1020.32(d)(3), except as specified in Sec. 1020.32(d)(2)(iii) of this
section:
(iii) Exceptions:
(A) For equipment manufactured prior to [date 1 year after date of
publication of the final rule in the Federal Register], during the
recording of images from a fluoroscopic image receptor using
photographic film or a video camera when the x-ray source is operated
in a pulsed mode.
(B) For equipment manufactured on or after [date 1 year after date
of publication of the final rule in the Federal Register], during the
recording of images from the fluoroscopic image receptor for the
purpose of providing the user with an image(s) after termination of the
exposure. However, the archiving of fluoroscopic or radiographic images
through the recording of such images in analog format with a video-tape
or video-disc recorder does not qualify as an exception.
(C) When a mode of operation has an optional high-level control and
the control is activated, in which case the equipment shall not be
operable at any combination of tube potential and current that will
result in an AKR in excess of 180 mGy per minute (vice 20 R/min
exposure rate) at the measurement point specified in
Sec. 1020.32(d)(3). Special means of activation of high-level controls
shall be required. The high-level control shall be operable only when
continuous manual activation is provided by the operator. A continuous
signal audible to the fluoroscopist shall indicate that the high-level
control is being employed.
(3) Measuring compliance. Compliance with paragraph (d) of this
section shall be determined as follows:
(i) If the source is below the x-ray table, the AKR shall be
measured at 1 centimeter above the tabletop or cradle.
(ii) If the source is above the x-ray table, the AKR shall be
measured at 30 centimeters above the tabletop with the end of the beam-
limiting device or spacer positioned as closely as possible to the
point of measurement.
(iii) In a C-arm type of fluoroscope, the AKR shall be measured at
30 centimeters from the input surface of the fluoroscopic imaging
assembly, with the source positioned at any available SID, provided
that the end of the beam-limiting device or spacer is no closer than 30
centimeters from the input surface of the fluoroscopic imaging
assembly.
(iv) In a C-arm type of fluoroscope having an SID less than 45 cm,
the AKR shall be measured at the minimum SSD.
(v) In a lateral type of fluoroscope, the air kerma rate shall be
measured at a point 15 centimeters from the centerline of the x-ray
table and in the direction of the x-ray source with the end of the
beam-limiting device or spacer positioned as closely as possible to the
point of measurement. If the tabletop is movable, it shall be
positioned as closely as possible to the lateral x-ray source, with the
end of the beam-limiting device or spacer no closer than 15 centimeters
to the centerline of the x-ray table.
(4) Exemptions. Fluoroscopic radiation therapy simulation systems
are exempt from the requirements set forth in paragraph (d) of this
section.
(e) [Reserved]
(f) Indication of potential and current. During fluoroscopy and
cinefluorography, x-ray tube potential and current shall be
continuously indicated. Deviation of x-ray tube potential and current
from the indicated values shall not exceed the maximum deviation as
stated by the manufacturer in accordance with Sec. 1020.30(h)(3).
(g) Source-skin distance. (1) Means shall be provided to limit the
source-skin distance to not less than 38 centimeters on stationary
fluoroscopes and to not less than 30 centimeters on mobile and portable
fluoroscopes. In addition, for fluoroscopes intended for specific
surgical application that would be prohibited at the source-skin
distances specified in this paragraph, provisions may be made for
operation at shorter source-skin distances but in no case less than 20
centimeters. When provided, the manufacturer must set forth precautions
with respect to the optional means of spacing, in addition to other
information as required in Sec. 1020.30(h).
(2) For mobile or portable C-arm fluoroscopic systems manufactured
on or after [date 1 year after date of publication of the final rule in
the Federal Register], having a maximum source-image receptor distance
of less than 45 centimeters, means shall be provided to limit the
source-skin distance to not less than 19 centimeters. Such systems
shall be labeled for extremity use only. In addition, for those systems
intended for specific surgical application that would be prohibited at
the source-skin distances specified in this paragraph, provisions may
be made for operation at shorter source-skin distances but in no case
less than 10 centimeters. When provided, the manufacturer must set
forth precautions with respect to the optional means of spacing, in
addition to other information as required in Sec. 1020.30(h).
(h) Fluoroscopic irradiation time, display, and signal. (1)(i)
Fluoroscopic equipment manufactured before [date 1 year after date of
publication of the final rule in the Federal Register], shall be
provided with means to preset the cumulative on-time of the
fluoroscopic tube. The maximum cumulative time of the timing device
shall not exceed 5 minutes without resetting. A signal audible to the
fluoroscopist shall indicate the completion of any preset cumulative
on-time. Such signal shall continue to sound while x-rays are produced
until the timing device is reset. Fluoroscopic equipment may be
modified in accordance with Sec. 1020.30(q) to comply with the
requirements of Sec. 1020.32(h)(2). When the equipment is modified, it
shall bear a label indicating the statement:
``Modified to comply with 21 CFR 1020.32(h)(2).''
(ii) As an alternative to the requirements of this paragraph,
radiation therapy simulation systems may be provided with a means to
indicate the total cumulative exposure time during which x-rays were
produced, and which is capable of being reset between x-ray
examinations.
(2) For x-ray controls manufactured on or after [date 1 year after
date of publication of the final rule in the Federal Register], there
shall be provided for each fluoroscopic tube:
(i) A display of the value and units of the irradiation time from
the beginning of a patient examination or procedure. This display shall
be visible at the fluoroscopist's working position throughout the
examination or procedure and after it ends. The display shall be able
to be reset to zero prior to the commencement of a new examination or
procedure, and it shall function independently of the audible signal
described in Sec. 1020.32(h)(2)(ii).
(ii) A signal audible to the fluoroscopist shall indicate the
passage of irradiation time during an examination or procedure. The
signal shall sound for at least one second at each interval of 5-
minutes duration of irradiation time.
(i) Mobile and portable fluoroscopes. In addition to the other
requirements of this section, mobile and portable fluoroscopes shall
provide an image receptor incorporating more than a simple fluorescent
screen.
(j) Display of last image hold (LIH). Fluoroscopic equipment
manufactured on or after [date 1 year after date of publication of the
final rule in the Federal Register], shall be equipped with means to
display an LIH radiograph following termination of the fluoroscopic
exposure.
[[Page 76094]]
(1) For an LIH radiograph obtained by retaining pretermination
fluoroscopic images, if the number of images and method of combining
images are selectable by the user, the selection shall be indicated
prior to initiation of the fluoroscopic exposure.
(2) For an LIH radiograph obtained by initiating a separate
radiographic exposure, if the techniques factors for the radiographic
exposure are selectable prior to the exposure, the combination selected
must be indicated prior to initiation of the fluoroscopic exposure.
(3) Means shall be provided to clearly indicate to the user whether
a displayed image is the LIH radiograph or fluoroscopy. Display of the
LIH radiograph shall be replaced by the fluoroscopic image concurrently
with reinitiation of fluoroscopic exposure, unless separate displays
are provided for the LIH radiograph and fluoroscopic images.
(4) The predetermined or selectable options for producing the LIH
radiograph shall be described in the information required by Sec.
1020.30(h). The information shall include a description of any
applicable technique factors for the selected option and the impact of
the selectable options on image characteristics and radiation dose.
(k) Displays of values of AKR and cumulative air kerma.
Fluoroscopic equipment manufactured on or after [date 1 year after date
of publication of the final rule in the Federal Register], shall
display at the fluoroscopist's working position values of AKR and
cumulative air kerma. The following requirements apply for each x-ray
tube used during an examination or procedure:
(1) The value displayed for AKR shall be in units of mGy/min and
shall represent the air kerma per unit time during fluoroscopy and
while recording during fluoroscopy.
(2) The value displayed for cumulative air kerma shall be in units
of mGy; shall include all contributions generated from fluoroscopic and
radiographic radiation; shall represent the total air kerma accrued
from the commencement of an examination or procedure and shall be
updated during the examination or procedure each time that fluoroscopic
or radiographic x-ray production is deactivated.
(3) During fluoroscopy and while recording during fluoroscopy, the
value and units of the AKR shall be displayed. Following fluoroscopy or
radiography, the value and units of the cumulative air kerma shall be
displayed.
(4) The display of the value of the AKR shall be clearly
distinguishable from the display of the value of the cumulative air
kerma.
(5) Values displayed for the AKR and cumulative air kerma shall be
determined for conditions of free-in-air irradiation at one of the
following reference locations specified according to the type of
fluoroscope. The reference location shall be identified and described
specifically in information provided to users according to Sec.
1020.30(h)(6)(iii).
(i) For fluoroscopes with x-ray source below the table, x-ray
source above the table, or of lateral type, the reference locations
shall be the respective locations specified in Sec. 1020.32(d)(3)(i),
(d)(3)(ii), or (d)(3)(v) for measuring compliance with air-kerma rate
limits.
(ii) For C-arm type fluoroscopes, the reference location shall be
15 centimeters from the isocenter toward the x-ray source along the
beam axis. Alternatively, the reference location shall be along the
beam axis at a point deemed by the manufacturer to represent the
intersection of the x-ray beam entrance surface and the patient skin.
(6) Means shall be provided to reset to zero the values of AKR and
cumulative air kerma prior to the commencement of a new examination or
procedures.
(7) The AKR and the cumulative air kerma shall not deviate from
their respective displayed values by more than +/-25 percent.
5. Amend Sec. 1020.33 by revising paragraph (h)(2) to read as
follows:
Sec. 1020.33 Computed tomography (CT) equipment.
* * * * *
(h) * * *
(2) For systems that allow high voltage to be applied to the x-ray
tube continuously and that control the emission of x-ray with a
shutter, the radiation emitted may not exceed 0.88 milligray (vice 100
milliroentgen exposure) in 1 hour at any point 5 centimeters outside
the external surface of the housing of the scanning mechanism when the
shutter is closed. Compliance shall be determined by measurements
average over an area of 100 square centimeters with no linear dimension
greater than 20 centimeters.
* * * * *
Dated: July 25, 2002.
Margaret M. Dotzel,
Associate Commissioner for Policy.
[FR Doc. 02-30550 Filed 12-9-02; 8:45 am]
BILLING CODE 4160-01-S