Effects of key parameters on the accuracy and precision of local pulse wave velocity measurement by ultrasound imaging

Quantification of arterial stiffness, such as pulse wave velocity (PWV), is increasingly used in the risk assessment of cardiovascular disease. Pulse wave imaging (PWI) is an emerging ultrasound-based technique to noninvasively measure the local PWV, instead of the global PWV as in conventional methods. In PWI, several key parameters, including the frame rate, number of scan lines, image width and PWV, play an important but still unclear role in the accuracy and precision of PWV measurement. In this study, computer simulations were performed to investigate the fundamental effects of these parameters on the PWV estimation. By applying different time delays on the pre-obtained pulse waveform based on specific PWI parameters, the pulse wave propagation along the artery was simulated and the ultrasound RF signals were generated from a convolutional image formation model. The PWI technique was applied to calculate the PWV at different values of key parameters. The performance is evaluated by measuring the bias, standard deviation (SD) and coefficient of determination (R²) of the estimated PWVs. 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 SD decreases while R² increases with number of scan lines and image width, indicating a better performance of the PWV estimation with a larger number of scan lines and image width. A higher value of PWV is found to deteriorate the PWV estimation. The quantitative effects of the key parameters obtained from this study may provide important guidelines for optimization of PWI parameters in vivo.