Particle Image Velocimetry to Evaluate Pulse Wave Velocity in Aorta Phantom with the lnD–U Method

Abstract

Purpose -Pulse Wave Velocity (PWV) is an indicator of arterial stiffness used in the prediction of cardiovascular disease such as atherosclerosis. Non-invasive methods performed with ultrasound probes allow one to compute PWV and aortic stiffness through the measurement of the aortic diameter (D) and blood flow velocity (U) with the lnD-U method. This technique based on in vivo acquisitions lacks validation since the aortic elasticity modulus cannot be verified with mechanical strength tests. Method -In the present study, an alternative validation is carried out on an aorta phantom hosted in an aortic flow simulator which mimics pulsatile inflow conditions. This in vitro setup included a Particle Image Velocimetry device to visualize flow in a 2D longitudinal section of the phantom, compute velocity fields (U), and track wall displacements in the aorta phantom to measure the apparent diameter (AD) variations throughout cycles. Results -The lnD-U method was then applied to evaluate PWV (5.92 ± 0.32 m/s) and calculate the Young's's modulus of the aorta phantom (0.66 ± 0.08 MPa). This last value was compared to the elasticity modulus (0.53 ± 0.07 MPa) evaluated with tensile strength tests on samples cut from the silicone phantom. Conclusion -Considering the uncertainties from the two methods, the measured elasticities are consistent and close to a 50-60 years old male aortic behavior. A comparison with in vivo data shows that the choice of silicone for the phantom material is a relevant and promising option to mimic the human aorta on in vitro systems.