Department of Physics and Astronomy, University of Western Ontario, 1151 Richmond Street, London, N6A 3K7 ON, Canada.
Department of Medical Biophysics, University of Western Ontario, 1151 Richmond Street, London, N6A 5C1 ON, Canada; Department of Surgery, University of Western Ontario, 268 Grosvenor Street, London, N6A 4V2 ON, Canada; Robarts Research Institute, University of Western Ontario, 1151 Richmond Street, London, N6A 5B7 ON, Canada; Bone and Joint Institute, University of Western Ontario, 1151 Richmond Street, London, N6G 2V4 ON, Canada.
Med Eng Phys. 2019 Mar;65:8-23. doi: 10.1016/j.medengphy.2018.12.023. Epub 2019 Feb 8.
The development of atherosclerosis at the carotid bifurcation is impacted by local variations in wall shear stress (WSS) magnitude and direction, as well as flow complexity within the vessel. In this study, stereoscopic particle image velocimetry (PIV) was used to investigate multidirectional WSS and disturbed flow for idealized models of the carotid bifurcation with varying eccentric stenosis of the internal carotid artery (ICA) and both Newtonian (N-fluid) and non-Newtonian (nN-fluid) blood analogues. Turbulence intensity (TI) was reduced with the nN-fluid compared to N-fluid for mild to moderate stenosis, and comparable for more severely stenosed (70%) models. Differences in maximum TI due to viscosity model ranged from 0.02 m/s to 0.06 m/s compared to much larger differences due to geometry of up to 0.29 m/s between mild and severe stenosis. The level of time-averaged WSS (TAWSS) increased with stenosis severity from 5 Pa to 32 Pa, and nN-fluid led to higher WSS on average than N-fluid counterparts. Regions of elevated oscillatory shear index (OSI) demarcated recirculation regions, and mean OSI in the ICA branch was reduced for nN-fluid models by 9-19% compared to N-fluid. Transverse WSS (transWSS) increased with WSS magnitude and again was higher in nN-fluid models. Surface area exposure to shear metrics indicated that a Newtonian viscosity assumption predicted larger regions of low and oscillatory WSS, while predicting reduced regions of high transWSS, in comparison to the more physiological shear thinning fluid.
颈动脉分叉处的动脉粥样硬化的发展受到壁面剪切应力（WSS）大小和方向的局部变化以及血管内流动复杂性的影响。在这项研究中，立体粒子图像测速（PIV）用于研究具有不同颈内动脉（ICA）偏心狭窄的颈动脉分叉理想模型的多向 WSS 和扰流，以及牛顿（N-流体）和非牛顿（nN-流体）血液模拟物。与 N-流体相比，nN-流体可降低轻度至中度狭窄的湍流强度（TI），对于更严重狭窄（70%）的模型，两者相当。由于粘度模型的最大 TI 差异范围为 0.02 m/s 至 0.06 m/s，而由于几何形状的差异最大可达 0.29 m/s，因此与轻度和重度狭窄之间的差异相比，差异要小得多。平均时均 WSS（TAWSS）随狭窄程度从 5 Pa 增加到 32 Pa，nN-流体导致的 WSS 平均高于 N-流体对应物。升高的振荡剪切指数（OSI）区域划定了再循环区域，与 N-流体模型相比，nN-流体模型中 ICA 分支的平均 OSI 降低了 9-19%。横向 WSS（transWSS）随 WSS 幅度增加而增加，nN-流体模型中的 transWSS 再次更高。表面剪切面积暴露于剪切指标表明，牛顿粘度假设预测的低和振荡 WSS 区域较大，而预测的高 transWSS 区域较小，与更生理剪切变稀流体相比。
