Mendieta Jessica Benitez, Fontanarosa Davide, Wang Jiaqiu, Paritala Phani Kumari, McGahan Tim, Lloyd Thomas, Li Zhiyong
School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, QLD, 4000, Australia.
Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, QLD, 4000, Australia.
Biomech Model Mechanobiol. 2020 Oct;19(5):1477-1490. doi: 10.1007/s10237-019-01282-7. Epub 2020 Jan 2.
The initiation and progression of atherosclerosis, which is the main cause of cardiovascular diseases, correlate with local haemodynamic factors such as wall shear stress (WSS). Numerical simulations such as computational fluid dynamics (CFD) based on medical imaging have been employed to analyse blood flow in different arteries with and without luminal stenosis. Patient-specific CFD models, however, have assumptions on blood rheology. The differences in the calculated haemodynamic factors between different rheological models have not been fully evaluated. In this study, carotid magnetic resonance imaging (MRI) was performed on six patients with different degrees of carotid stenosis and two healthy volunteers. Using the 3D reconstructed carotid geometries and the patient-specific boundary conditions, CFD simulations were performed by applying a Newtonian and four non-Newtonian models (Carreau, Cross, Quemada and Power-law). WSS descriptors and pressure gradient were analysed and compared between the models. The differences in the maximum and the average oscillatory shear index between the Newtonian and the non-Newtonian models were lower than 12.7% and 12%, respectively. The differences in pressure gradient were also within 15%. The differences in the mean time-averaged WSS (TAWSS) between the Newtonian and Cross, Carreau and Power-law models were lower than 6%. In contrast, a higher difference (26%) was found in Quemada. For the low TAWSS, the differences from the Newtonian to the non-Newtonian models were much larger, in the range of 0.4-31% for Carreau, 3-22% for Cross, 5-51% for Quemada and 10-41% for Power-law. The study suggests that the assumption of a Newtonian model is reasonable when the overall flow pattern or the mean values of the WSS descriptors are investigated. However, the non-Newtonian model is necessary when the low TAWSS region is the focus, especially for arteries with severe stenosis.
动脉粥样硬化是心血管疾病的主要病因，其发生和发展与局部血流动力学因素如壁面切应力（WSS）相关。基于医学成像的数值模拟，如计算流体动力学（CFD），已被用于分析有无管腔狭窄情况下不同动脉中的血流。然而，针对特定患者的CFD模型对血液流变学有假设。不同流变学模型之间计算得到的血流动力学因素差异尚未得到充分评估。在本研究中，对6例不同程度颈动脉狭窄患者和2名健康志愿者进行了颈动脉磁共振成像（MRI）检查。利用三维重建的颈动脉几何形状和特定患者的边界条件，应用牛顿模型和四种非牛顿模型（卡罗厄模型、克罗斯模型、凯马达模型和幂律模型）进行了CFD模拟。对各模型之间的WSS描述符和压力梯度进行了分析和比较。牛顿模型与非牛顿模型之间最大振荡剪切指数和平均振荡剪切指数的差异分别低于12.7%和12%。压力梯度差异也在15%以内。牛顿模型与克罗斯模型、卡罗厄模型和幂律模型之间的平均时间平均壁面切应力（TAWSS）差异低于6%。相比之下，凯马达模型的差异较高（26%）。对于低TAWSS情况，从牛顿模型到非牛顿模型的差异要大得多，卡罗厄模型在0.4 - 31%范围内，克罗斯模型在3 - 22%范围内，凯马达模型在5 - 51%范围内，幂律模型在10 - 41%范围内。该研究表明，在研究整体血流模式或WSS描述符的平均值时，假设牛顿模型是合理的。然而，当关注低TAWSS区域时，尤其是对于严重狭窄的动脉，非牛顿模型是必要的。
