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Doppler Ultrasound - http://ej.rsna.org/ej3/0079-98.fin/doppler.htm
The Doppler effect is a change in the frequency of a wave, resulting from motion of the wave source or receiver, or in the case of a reflected wave, motion of the reflector. In medicine, Doppler US is used to detect and measure blood flow, and the major reflector is the red blood cell. |