Ultrasonic Imaging.

Ultrasonic imaging is a medical diagnostic tool that visualizes the internal structures of the body with a high-frequency sound beam. In contrast to X-rays, which produce harmful, ionizing radiation, ultrasound has no known harmful effects. The heart of the device is the transducer, which transmits the sound beam to and receives an echo from internal structures. Structures within the body reflect the sound beam to different degrees. Sound passes through liquid readily, is reflected to some degree by muscle, and is strongly reflected by bone. Ultrasound is commonly used to visualize the developing fetus within the uterus. The amniotic fluid surrounding the fetus transmits the sound beam to the fetus and its internal structures.