Ultrasonography involves transmitting ultrasound waves into the body. Body tissue reflects the sound to varying degrees, thereby producing a sound image, or sonogram. Unlike X-rays, ultrasound examinations are harmless. Painless ultrasound examinations can therefore be performed safely even on children and pregnant women.

Ultrasonography can be used to examine almost any organ. It is used most commonly to examine the abdominal organs, the thyroid gland, the lymph nodes, the female breast and the tendons of the musculoskeletal system. It also provides important information that can help with early detection of cancer and cancer aftercare. Ultrasonography can easily and safely show the target area when inserting needles for diagnostic (tissue removal) or therapeutic (painkiller injection) purposes. Doppler sonography can also highlight vascular constrictions or obstructions.