Abstract
The pulse wave velocity (PWV) has been used clinically as an index in order to evaluate arterial distensibility and the grade of atherosclerosis quantitatively. But the conventional method of PWV measurement has relied upon averages between the carotid and femoral arteries, inapplicable to any specific regional site. We propose a new method using Doppler techniques which can measure PWV accurately over closely spaced sampling sites just a few centimeters apart. We investigated the accuracy of this system at an ultrasonic frequency of 7.5MHz. We employed a Pulsatile flow circuit model in which the arterial wall was simulated by silicone tube. Local pulse wave velocity employs a signal processing procedure to increase the coherence between these two Doppler signals (5cm, 3cm, 2cm, 1cm) and involves the complex cross correlation analysis of these processed signals. We investigated the influence of blood flow pattern change when the pulse propagation length is fixed at 3cm. The longer the distance traveled, the longer the propagation time of the pulse wave. Upon examination of the standard deviation of PWV at each measured distance, we found a significant difference (p<0.05) between 1cm and 2cm. Changes induced in blood flow pattern did not affect pulse propagation time. The combination of noninvasive Doppler ultrasonography for measuring pulse wave propagation velocity over very short distance of more than two centimeters and complex cross-correlation analysis give us the potential means for evaluating local arterial distensibility.
