ultrasonic waves

high frequency sound waves (above 20 kHz), beyond the range of the human ear. Ultrasound is used to examine the body's organ, ducts, etc, in addition to assessing the progress of a developing FOETUS . The patient is not submitted to harmful radiation as with other techniques and no contrast medium is required. It can be used to examine the liver, kidney, bladder, pancreas and ovaries and is used in diagnosing brain tumours. The vibrations of the sound waves can be used in other ways, e.g. breaking up kidney stones (renal calculi).