Physiological flow characterization in elastic vessel phantom using Ultrasonic Particle Image Velocimetry

Abstract

Altered vascular stiffness can influence hemodynamics in the long-term vessel stiffening process, which can be aggravated in a viscous cycle. Elucidation of how vascular stiffness and hemodynamics interact with each other, underpins insights into cardiovascular disease and its diagnosis. In our ultrasound measurement study, the affect of arterial stiffness on hemodynamics is investigated by simulated physiological flow in experimental elastic vessel phantoms based on a 10wt% polyvinyl alcohol aqueous solution that solidifies when subjected to up to 8 freeze-thaw (f-t) cycles. As the vascular phantoms are subjected to these f-t cycles, their Young's modulus, speed of sound, and attenuation coefficients increase. Elastic phantoms of constant inner diameter were subjected to pressure increase in a fluid circuit, resulting in diameter and pulse pressure increments. It can be shown that increased vascular stiffness causes degraded vasomotion and elevated pulse pressure, indicating degradation in the function of blood pumping. Peak velocity measured by Doppler and Echo Particle Image Velocimetry (EchoPIV) techniques have bias less than 5% during the whole cardiac cycle. The EchoPIV results demonstrate parabolic velocity profiles for all three phantoms. Measured peak velocities demonstrate that the stiffer vessel has a smaller peak-to-peak value of velocity, while showing up a slight difference for their shear rate due to their relatively small stiffness differences. In summary, our experiments show that vascular stiffness has influence on vasomotion, flow pressure, flow velocity, and shear rate.