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.
Multigon (USA) http://www.multigon.com/
Transcranial Doppler (TCD) - non invasive ultrasound technology used to evaluate blood flow velocity in the major basal intracranial arteries
Vmed Technology, Inc. http://www.vmedtech.com/vacupads.htm
hand-held, 9V battery operated ultrasonic Doppler that has been used in human and animal applications for over 20 years. Models are available for fetal and blood flow detection both in humans and animals. Doppler signals are heard with a stethoscope style headset.
