Application of stereoscopic PIV for hemodynamic studies of life-sized carotid artery models under pulsatile flow condition

Abstract

One of the major causes of ischemic stroke is embolism of thrombi (i.e. blood clots) that are formed at the site of the atherosclerotic plaque in the carotid artery bifurcation. Certain hemodynamic factors, such as flow disturbances, shear stress forces, and recirculation are linked to thrombosis by enhancing and facilitating platelet activation and aggregation [1, 2]. Any alterations of the local flow patterns that can, in turn, induce altered hemodynamic factors can impact the level of thrombotic activity. Previous clinical studies have shown the association of certain geometrical features of the plaque, namely severity of stenosis (i.e. narrowing), plaque eccentricity (symmetry), and plaque ulceration (irregular surface) to the frequency of cerebrovascular events [3, 4]. As a gold-standard experimental technique, particle image velocimetry (PIV) can provide detailed analysis of spatially and temporally evolving flows. This technique has extensively been applied to hemodynamic studies, primarily to investigate the potential of thrombosis in mechanical heart valves (ref). To date, only three PIV studies (excluding echo PIV studies) have been reported in carotid artery models; Bale-Glickman et al. [5] applied planar PIV to two patientspecific stenosed carotid artery models, Vetel et al. [6] studied flow in a patient-specific model of a healthy carotid artery using stereo PIV, and Buchmann et al. [7] studied a healthy carotid artery model and compared results using tomographic and stereoscopic PIV. All studies were conducted assuming steady inlet flow; although they provide a baseline understanding of flow patterns, pulsatile flow conditions strongly impact the flow dynamics, introducing flow instabilities and high temporal gradients. We have developed a flow-measurement system applying stereoscopic PIV in a family of life-sized carotid artery models, representing a range of disease progression, under physiologically realistic flow conditions in order to characterize stenosed flow features and investigate the impact of the geometrical features of the plaque on downstream flow patterns. A detailed description of the experimental design features and challenges are described, along with sample results. To demonstrate the capability of this system, flow features extracted from a 70% concentrically stenosed model are presented.