Tomographic PIV analysis of physiological flow conditions in a patient-specific arteriovenous fistula

The arteriovenous fistula (AVF), which is a vasculature created for end-stage renal disease patients who require haemodialysis, is susceptible to many vascular diseases. It is well known that disturbed hemodynamics is a factor in the initiation of vascular disease; however, only a limited number of experimental studies have been conducted to assess the flow behaviour within the AVF. The current study is an investigation of the complex three-dimensional flow within a physiological AVF geometry, using tomographic particle image velocimetry. To this end, a benchtop model of a patient-specific geometry was created by casting silicone around a soluble 3D print of the vessels. The patient-specific boundary conditions were reproduced by driving a refractive-index matched working fluid from a pulsatile pump, which was connected to the model via a tubing network inclusive of valves and compliance chambers. The seeded working fluid was illuminated with a 1 kHz double-pulsed laser, and four high-speed cameras placed at optimised locations were used to capture the particle images, with the volume reconstructions refined by a 3D internal mask created using morphological operations. The velocity magnitude contour plots of the resulting vector field revealed two zones of low velocity in the anastomosis, while locations of high turbulent kinetic energy are observed in the anastomosis and venous regions. These results suggested that the collision of the two opposing inlet flows and the curvature at the anastomosis cause disturbance in the flow that is carried downstream.