Images are created by sending sound waves into the body and then listening for their echo. This is done with a transducer, a hand-held device that converts one form of energy to another and a computer, which will display the data. When the transducer is pressed against the skin, small pulses of inaudible, high-frequency sound waves are directed into the body. As these sound waves bounce off internal organs, fluids, and tissues, the transducer receiver collects the tiny changes in the pitch and direction of the sound. The data is then displayed by a computer, as a real-time (moving) picture on the monitor.
In some cases, ultrasounds are done internally. To do this, the transducer is attached to a probe and then inserted into a natural opening in your body, such as the esophagus, rectum, or vagina.