What is ultrasound?

Ultrasound, also called sonography, uses high-frequency sound waves that bounce off tissues to create an image of the inside of the body.

How does it work?

As the sound waves pass through the body, echoes are produced that can determine the shape of an organ, of tissues and their consistency (solid, fluid or composed of both.) The images are captured and stored on videotape, but they also can be "frozen" and printed as still photos. Ultrasound is useful in imaging the heart, liver, gallbladder, spleen, pancreas, kidneys and bladder. It is also used to monitor the growth and well being of a fetus. Because it provides real-time images, it can be used as a guide for needle biopsies and other minimally invasive tests.

What does the equipment look like?

The device includes a fixed console with a video display screen and a hand-held transducer, about the size of a bar of soap, that is held against the skin and picks up the radio waves. The transducer is connected to the main unit by a cord. The image is visible immediately on the computer screen and can sometimes be seen by the patient.

How should I prepare for ultrasound?

Depending on the type of exam, your doctor may ask you to refrain from eating and drinking anything for up to 12 hours before the exam, or you may receive other instructions. Wear comfortable, loose-fitting clothing.

What will I experience during the ultrasound?

Ultrasound is fast (less than 30 minutes), painless and non-invasive. As you lie on your back on the examining table, the technician spreads a warm gel - which helps the transducer make contact with the skin and eliminates air pockets between the skin and the transducer - on the part of the body to be studied. You may experience pressure as the technician sweeps the transducer across the skin to image the area that is the focus of the study.

How will I get the results?

A radiologist, a physician who is trained to interpret medical images, reviews test results before sending them, along with a written report, to your personal physician. In some cases, he or she will discuss the results with you. Results are usually available from your physician's office within a few days.

What are the benefits and risks of ultrasound?

No radiation is used and ultrasound is widely available, easy to use and relatively inexpensive. There is no known risk.

Ultrasound has difficulty in penetrating bone, so other diagnostic tests are usually recommended in the case of bone disorders and sports injuries. It is not as effective for use with obese patients, because tissue weakens the sound waves as they pass through the body.