What is the test?
Ultrasound uses sound waves instead of radiation to generate snapshots or moving pictures of structures inside the body. This imaging technique works in a manner similar to radar and sonar, developed in World War II to detect airplanes, missiles, and submarines that were otherwise invisible. After coating a small area of your skin with a lubricant to reduce friction, a radiologist or ultrasound technician places an ultrasound transducer, which looks like a microphone, on your skin and may rub it back and forth to get the right view. The transducer sends sound waves into your body and picks up the echoes of the sound waves as they bounce off internal organs and tissue. A computer transforms these echoes into an image that is displayed on a monitor.
Doppler ultrasound is a variation of this technique that not only shows internal structures but also examines the flow of blood through blood vessels. Using the Doppler effect—the change in the frequency of sound or light waves as they bounce off a moving object—this kind of ultrasound produces an image of blood in motion.
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