A 3-D PW ultrasonic Doppler flowmeter: theory and experimentalcharacterization

摘要

A complete 3-D ultrasonic pulsed Doppler system has been developednto measure quantitatively the velocity vector field of a fluid flownindependently of the probe position. The probe consists of four 2.5 MHznpiezocomposite ultrasonic transducers (one central transmitter and threenreceivers separated by 120°) to measure the velocity projectionsnalong three different directions. The Doppler shift of the threenchannels is calculated by analog phase and quadrature demodulation, thenndigitally processed to extract the mean velocity from the complexnspectrum. The accuracy of the 3-D Doppler technique has been tested on anmoving string phantom providing an error of about 4% for both amplitudenand direction with an acquisition window of 100 ms