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MAVIS is a multichannel direction-resolving pulsed-wave ultrasonic doppler flow detector with imaging capability. The instrument can provide anterior-posterior, cross-sectional, and lateral views of blood vessels as well as the measurement of the velocity profiles across the vessel lumen. The major advantage over single-channel devices is the speed of measurement.
The system incorporates a position resolver, mechanically coupled to the ultrasound transducer. When the ultrasound beam is directed towards a blood vessel the presence of a flow signal is recorded as a spot on a storage monitor at a position corresponding to that of the probe. As the transducer is moved over the skin overlying the vessel, an image of its projection on the skin surface is generated on the screen.
MAVIS has 30 flow detection channels, each measuring the magnitude and direction of blood flow along the beam axis. The distance between the transducer and the first of the 30 detection points and the separation of the points are both variable. This allows superficial vessels to be imaged with a resolution of about 1 mm.
The beam angle is calculated using a microprocessor. Three cross-sectional scans about half a centimetre apart are required for this measurement. The distortion of the velocity profiles in the smaller vessels due to the finite size of the sampling volumes is also corrected by means of the microprocessor.
Such devices would be used in the investigation of arterial disease.
Content and Design Copyright 2000 Dr. Malcolm C Brown. See Title Page for more details