Effects of key parameters on the performance of local pulse wave velocity measurement: Theroretial analysis and in-vivo validation

The predictive value of pulse wave velocity (PWV) for various cardiovascular diseases has been demonstrated in many studies. By means of ultrasound imaging, local PWV, instead of global PWV as in conventional methods, can be measured noninvasively. The accuracy and precision of local PWV measurement have not been fully investigated and several key parameters (i.e. frame rate, number of scan lines and image width) are shown to play an important but still unclear role on PWV measurement. In this study, the quantitative effects of these parameters were investigated with theoretical analysis and in-vivo experiments. The theoretical relationship between the standard deviation (SD) of the PWV estimation and some key parameters (number of scan lines, image width and PWV value) and the variance of characteristic time-point identification (or time-shift estimation) was derived first. PWVs were then estimated from in-vivo RF signals at different values of frame rate, number of scan lines, and image width. The results show that PWVs can be correctly measured when the frame rate is higher than a certain value, below which the estimated PWVs become inaccurate. The performance of PWV measurement is found to improve with increased number of scan lines and image width. Overall, a larger number of scan lines and image width with a sufficiently high frame rate is preferred. The in-vivo results are in in good agreement with the theoretical analysis as well as our previous simulation results. Our quantitative findings can provide important guidelines for parameters optimization in ultrasound-based local PWV measurement.