PULSATILE VELOCITY DISTRIBUTION AND WALL SHEAR RATE MEASUREMENT USINGPULSED DOPPLER ULTRASOUND

Instantaneous pulsatile velocity profiles were measured in a cylindric al tube using a 20 MHZ pulsed Doppler ultrasound system. The spatial r esolution of the device was improved with deconvolution using a proced ure which employed frequency-domain windowing to suppress high-frequen cy noise. After deconvolution both the instantaneous velocity profiles and flow waveforms were compared with established theoretical predict ions and good agreement was obtained. The average error in a velocity measurement was 7.9 +/- 0.9%, and the average error in the flow rate w as 4.7 +/- 1.7%. The wall shear rate was determined from the gradient of the velocity profile both before and after deconvolution. The resul ts were compared to the theoretical value of wall shear rate to quanti fy the accuracy of the technique under pulsatile flow conditions. Alth ough the velocity profiles agreed well with theory, the wall shear rat e was obtained less accurately. The average error in the mean wall she ar rate and peak-to-peak wall shear rate was 28 +/- 7% and 11 +/- 3%, respectively. However, some of this discrepancy, was attributed to the method of evaluation. In all cases deconvolution significantly improv ed the accuracy of the wall shear rate determination.