ultrasonics /-son″iks/ , the science dealing with sound waves having frequencies above the approximately 20-kHz range of human hearing. Ultrasound evolved from the World War II sonar underwater detection apparatus and was first adapted for medical diagnostic purposes in the 1950s. It uses a transducer and generates very short pulses of high-frequency sound that are transmitted into the body. Echoes from interfaces within the body are displayed on a cathode ray tube so that images of normal and abnormal structures can be viewed.
