Ultrasound Imaging of the Musculoskeletal System

What does the equipment look like?

The equipment consists of a transducer and a monitoring system. The transducer is a small, hand-held device that resembles a microphone. The radiologist or sonographer spreads a lubricating gel on the area being examined and then presses this device firmly against the skin.

The ultrasound image is immediately visible on a nearby screen that looks much like a computer or television monitor. The radiologist or sonographer watches this screen during an examination and captures representative images for storage. Often the patient is able to see it as well.

An example of the ultrasound equipment that may be used is shown at the top of this page.

Top

How does the procedure work?

Ultrasound imaging is based on the same principles involved in the sonar used by bats, ships at sea, and anglers with fish detectors. As a controlled sound bounces against objects, its echoing waves can be used to identify how far away the object is, its shape, how large it is, and its internal consistency (fluid, solid, or mixed).

The ultrasound transducer functions as both a loudspeaker (to create the sounds) and a microphone (to record them). When the transducer is pressed against the skin, it directs a stream of inaudible, high-frequency sound waves into the body. As the sound waves echo from the body's fluids and tissues, the sensitive microphone in the transducer records tiny changes in the sound's pitch and direction. These signature waves are instantly measured and displayed by a computer, which in turn creates a real-time picture on the monitor. The live images of the examination can be recorded on videotape. In addition, still frames of the moving picture are usually "frozen" to capture a series of images.

Top

How is the procedure performed?

The patient is positioned on an examination table that can tilt and move. A clear gel is applied to the area that will be examined. The gel helps the transducer make a secure contact and eliminates air pockets between the transducer and the skin, since the sound waves cannot penetrate air. The radiologist then presses the transducer firmly against the skin and sweeps it back and forth to image the area of interest, reviewing the images on the monitor and capturing "snapshots" as required.

When the examination is complete, the patient may be asked to dress and wait while the ultrasound images are reviewed, either on film or on a monitor. Often, though, the sonographer or radiologist is able to review the ultrasound images in real time as they are acquired, and the patient can be released immediately.

Top

What will I experience during the procedure?

Most ultrasound studies are relatively quick and well-tolerated by the patient. If scanning is performed over an area of tenderness, there may be minor pain associated with the procedure. Otherwise the procedure is painless. You will be either lying or sitting on an examining table that may be tilted or moved to provide access to the area that will be imaged. The sonographer or radiologist will spread some gel on your skin and then press the transducer firmly against your body, moving it until the desired images are captured. Most exams take 45 minutes or less.

Top

Who interprets the results and how do I get them?

A radiologist, who is a physician experienced in ultrasound and other radiology examinations, will analyze the images and send a signed report with his or her interpretation to the patient's personal physician. The patient receives ultrasound results from the referring physician who ordered the test results. New technology also allows for distribution of diagnostic reports and referral images over the Internet at some facilities.

Top

What are the benefits vs. risks?

Benefits

Ultrasound scanning is usually painless and noninvasive.

Ultrasound is widely available and easy to use.

Ultrasound imaging uses no ionizing radiation.

Ultrasound provides real-time imaging, making it a good tool for guiding minimally invasive procedures, such as cortisone injections, needle biopsies and aspiration of fluid in joints or elsewhere.

Unlike the strong magnetic field of magnetic resonance imaging (MRI), ultrasound is not affected by cardiac pacemakers, ferromagnetic implants or fragments within the body. Ultrasound is also an excellent alternative to MRI for claustrophobic patients.

Ultrasound may actually have advantages over MRI in seeing tendon structure, which is better appreciated by ultrasound than MRI.

Risks

For standard diagnostic ultrasound there are no known harmful effects on humans.

Top

What are the limitations of Ultrasound Imaging of the Musculoskeletal System?

Ultrasound has difficulty penetrating bone and, therefore, can only see the outer surface of bony structures and not what lies within and beyond. For visualizing internal structure of bones or certain joints, other imaging modalities, such as MRI, should be selected.

Top

To locate a medical imaging or radiation oncology provider in your community, you can search the ACR-accredited facilities database.

This procedure is reviewed by a physician with expertise in the area presented and is further reviewed by committees from the American College of Radiology (ACR) and the Radiological Society of North America (RSNA), comprising physicians with expertise in several radiologic areas.