Feasibility and validation of 4D Pulse wave Imaging (PWI) in vitro: 3D automated estimation of regional Pulse Wave Velocity vector

Pulse wave Imaging (PWI) is a noninvasive technique for tracking the propagation of the pulse waves along the arterial wall. Estimation of regional Pulse Wave Velocity (PWV) using 2D long-axis views of arterial vessels assumes propagation parallel to the imaging plane. 3D ultrasound imaging would aid in objectively estimating the PWV vector. The aims of this study were to introduce a novel method for PWV estimation along the direction of the wave propagation, and validate it in phantoms. Silicone vessel phantoms consisting of stiff and soft segments along the longitudinal axis were constructed and embedded into a very soft silicone background. A 2D array with a center frequency of 2.5 MHz was used to image each section using plane wave transmissions. Static and dynamic mechanical testing was used for PWV validation. The propagation was successfully visualized in 3D. PWVs were estimated in both the stiff (3.42 ± 0.23 m/s) and soft (2.41 ± 0.07 m/s) sections of the phantoms. Good agreement was found between the estimated PWVs and the corresponding static testing values (stiff. 3.41 m/s, soft. 2.48 m/s). Additionally, PWI-derived vessel compliance values were validated with dynamic testing. Thus, 4D PWI was successfully implemented and validated in silicone phantoms with plane waves at high volume rates.