An ultrasound test sends and receives high-frequency sound waves to create images of internal organs or tissues. Sound waves pass into the tissues of the area being examined. These sound waves are reflected (bounced back), recorded and displayed on a computer screen or television-type monitor. The technology used in ultrasound in similar to sonar.

Ultrasound may be used to diagnose a number of medical conditions, including cancer. It creates images of soft tissue organs, such as the gall bladder, liver, heart, kidney and female reproductive organs. Ultrasound is especially useful in diagnosing cancer when a tumor is located in soft tissue and it is unclear whether an abnormality is a cyst (sac of fluid) or a solid mass.

The images created by an ultrasound are considered to be less clear than those from CAT scans (computed axial tomography) or MRIs (magnetic resonance imaging). They can provide different information than these tests, however, and can be used for a wide array of reasons. Unlike CAT scans and MRI, ultrasound does not use any form of radiation. Because it is fast, noninvasive and relatively inexpensive, ultrasound is frequently used to help with the diagnosis and treatment of certain cancers.