ultrasound scanningA method of body imaging based on the reflectivity of sound. By using very high frequency (ultrasonic) sound the wavelengths are brought down to the necessary small dimensions. Piezo-electric transducers are used both to generate the waves and to pick up the reflected sound. Ultrasound scanning is believed to be completely safe and is widely used in obstetrics as well as in other disciplines. It can show the position of the placenta, reveal twins at an early stage, show the size and sex of the fetus and detect major fetal abnormalities such as ANENCEPHALY and SPINA BIFIDA. It can measure rates of blood flow in the fetus and can detect certain forms of congenital heart disease. Ultrasound is also widely used to scan fluid-filled organs, especially the heart. Echocardiography can reveal the heart's action in detail. Doppler ultrasound provides essential information on blood flow. Intravenously-injected microbubble agents increase the reflectivity of blood many times and greatly widen the scope of ultrasound scanning.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005