Doppler ultrasonic flowmeter


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Doppler ultrasonic flowmeter

 [dop´ler]
a device for measuring blood flow that transmits sound at a frequency of several megahertz downstream along the flowing blood. Some of the sound waves are reflected by the moving red blood cells back toward the transducer. The difference in pitch between the transmitted and reflected sounds is produced as an audible tone and is proportional to the velocity of blood flow. Called also Doppler ultrasound flowmeter.

A flowmeter can be incorporated into a stethoscope so that qualitative and quantitative measurements of the flow of blood through arteries and veins can be obtained. The Doppler flowmeter is capable of recording very rapid pulsatile changes in flow as well as steady flow; hence, it is helpful in assessing intermittent claudication, thrombus obstruction of deep veins, and other abnormalities of blood flow in the major arteries and veins.

There are various different types: a laser Doppler flowmeter is one in which blood flow is examined by a laser beam; the light is shifted by moving objects, mostly red blood cells, in accordance with the Doppler effect and the scattered light detected with a photodetector. A transcranial Doppler flowmeter is one that evaluates cerebral blood flow in the six intracranial arteries to assist in diagnosis of brain injury. One important use is for the detection of vasospasm. It can also be used for the assessment of patients who are suspected to be brain dead or have suffered head trauma, and for monitoring of patients during surgery. The results of a TCD test are displayed on a color monitor and may be printed out.
transcranial Doppler ultrasonic flowmeter (TCD ultrasound flowmeter) an apparatus that evaluates cerebral blood flow in the six intracranial arteries to assist in diagnosis of brain injury. One important use is for the detection of vasospasm. It can also be used for the assessment of patients who are suspected to be brain dead or have suffered head trauma, and for monitoring of patients during surgery. The results of a TCD test are displayed on a color monitor and may be printed out.
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