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Currently
some medical imaging facilities are promoting a new use of computed
tomography (CT), also called computerized axial tomography (CAT)
scanning. This use is referred to as whole-body CT scanning or whole-body
CT screening, and it is marketed as a preventive or proactive healthcare
measure to healthy individuals who have no symptoms or suspicion
of disease. At this time the FDA knows of no data demonstrating
that whole-body CT screening is effective in detecting any particular
disease early enough for the disease to be managed, treated, or
cured and advantageously spare a person at least some of the detriment
associated with serious illness or premature death. Any such
presumed benefit of whole-body CT screening is currently uncertain,
and such benefit may not be great enough to offset the potential
harms such screening could cause.
Public health agencies and national medical and professional societies-the
American
College of Radiology, the American
College of Cardiology / American Heart Association, the
American
Association of Physicists in Medicine, the Health
Physics Society and the Agency for Healthcare Research
and Quality's U.S.
Preventive Services Task Force - do not recommend CT
screening.
CT is a diagnostic imaging procedure that uses
x rays to obtain cross-sectional images of the body. Since its introduction
and rapid adoption into medicine in the mid-1970s, CT has become recognized
as a valuable medical tool for the diagnosis of disease, trauma, or abnormality
and for planning, guiding, and monitoring therapy.
Important information regarding whole-body CT screening:
- Such screening provides uncertain benefit
with potential for some risk - The most likely outcomes of CT
screening of a healthy person with no symptoms of illness are:
- Normal findings or
- Suspicious findings requiring follow-up tests
Normal findings carry the possibility of inaccuracy and false reassurance.
For suspicious findings, follow-up may involve simple, non-invasive
testing. It may also involve invasive procedures associated with surgical
risks of anesthesia, bleeding, infection, scarring, or it may entail
additional radiological exams, associated with radiation risk and
the potential risk of allergic reaction to injected contrast material.
In any case, it is unlikely that CT screening will benefit an individual
lacking signs or symptoms of disease by detecting a serious disease
early enough to treat it and alter the outcome significantly.
- Radiation Dose - CT screening subjects
the individual screened to radiation exposure from x rays. The
dose a patient receives during a typical CT procedure is generally
much larger than the radiation doses associated with most conventional
x-ray imaging procedures. The principal risk associated with the radiation
dose resulting to a person from a CT procedure is the small possibility
of developing a radiation-induced cancer some time later in that person's
life. For a patient with a medical need, the benefit of a diagnostic
or therapeutic CT procedure recommended by a physician normally far
exceeds the small cancer risk associated with a CT procedure. For a
person without symptoms, CT screening is unlikely to discover serious
disease, and the potential harm to the individual may be greater than
the presumed benefit.
- Scientific Studies - There are no data demonstrating that whole-body
CT screening of individuals without symptoms provides a greater probability
of benefit than harm. Nor is there any scientific study known to be
underway to develop such data. Although there are several
ongoing investigational studies of the effectiveness of using CT
to screen people, the studies are focused on high-risk groups for specific
diseases (e.g., cigarette smokers for lung cancer). In such studies
only a limited portion of the body is irradiated, not the whole body,
and only screening for a specific type of disease is being evaluated,
rather than screening for just anything that might be found anywhere
in the body.
- No Food and Drug Administration (FDA)
Approval of CT for Screening - Statements by CT imaging facilities
that imply FDA "approval," "clearance," or "certification"
of CT for screening procedures misrepresent the actual situation. FDA
has never approved or cleared or certified any CT system specifically
for use in screening (i.e., of individuals without symptoms), because
no manufacturer has ever demonstrated to the FDA that their CT scanner
is effective for screening for any disease or condition.
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