An ultrasound test uses high-frequency, low-energy sound waves to create images of internal organs or tissues. Some waves sent by the ultrasound machine pass through tissues, and others bounce back. Different quantities of waves bounce back depending upon density of the tissue, thus helping to distinguish different tissues. As sound waves bounce back, they are recorded and displayed on a computer screen or television-type monitor.

The image created is considered to be less clear than those from other imaging tests such as a CAT scan or MRI. However, ultrasound is often used for a wide array of procedures because it is fast, generally noninvasive, relatively inexpensive and more specific than other tests for some conditions.

Ultrasound technology can help a physician find the source of chest pain, abdominal pain, pelvic pain and sexual pain. It can be used in diagnosing and monitoring the progress of numerous conditions, such as prostate enlargement (benign prostatic hyperplasia), tendon and muscle ruptures, kidney stones, lupus, osteoporosis, rheumatoid arthritis and some cancers.

Ultrasound can also be used to monitor fetal development, and to help guide needles and other instruments under the skin and to the target area.

In addition to diagnostic ultrasound, there is therapeutic ultrasound, which employs higher frequencies of sound to produce heat. This form of thermotherapy can help control muscle spasms, pain, inflammation and other problems.