Laboratory of Hemodynamics and Cardiovascular Technology, School of Life Science, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
Ann Biomed Eng. 2011 Feb;39(2):850-63. doi: 10.1007/s10439-010-0200-6. Epub 2010 Nov 2.
Intracranial aneurysms may be treated by flow diverters, alternatively to stents and coils combination. Numerical simulation allows the assessment of the complex nature of aneurismal flow. Endovascular devices present a rather dense and fine strut network, increasing the complexity of the meshing. We propose an alternative strategy, which is based on the modeling of the device as a porous medium. Two patient-specific aneurysm data sets were reconstructed using conventional clinical setups. The aneurysms selection was done so that intra-aneurismal flow was shear driven in one and inertia driven in the other. Stents and their porous medium analog were positioned at the aneurysm neck. Physiological flow and standard boundary conditions were applied. The comparison between both approaches was done by analyzing the velocity, vorticity, and shear rate magnitudes inside the aneurysm as well as the wall shear stress (WSS) at the aneurysm surface. Simulations without device were also computed. The average flow reduction reaches 76 and 41% for the shear and inertia driven flow models, respectively. When comparing the two approaches, results show a remarkable similarity in the flow patterns and magnitude. WSS, iso-velocity surfaces and velocity on a trans-sectional plane are in fairly good agreement. The root mean squared error on the investigated parameters reaches 20% for aneurysm velocity, 30.6% for aneurysm shear rate, and 47.4% for aneurysm vorticity. It reaches 20.6% for WSS computed on the aneurysm surface. The advantages of this approach reside in its facility to implement and in the gain in computational time. Results predicted by the porous medium approach compare well with the real stent geometry model and allow predicting the main effects of the device on intra-aneurismal flow, facilitating thus the analysis.
颅内动脉瘤可以通过血流导向装置进行治疗，替代支架和线圈联合治疗。数值模拟可以评估动脉瘤血流的复杂特性。血管内装置具有相当密集和精细的支柱网络，增加了网格的复杂性。我们提出了一种替代策略，即将装置建模为多孔介质。使用传统的临床设置重建了两个特定于患者的动脉瘤数据集。选择动脉瘤，以便一个动脉瘤内的流动是剪切驱动的，另一个动脉瘤是惯性驱动的。支架及其多孔介质模拟物被放置在动脉瘤颈部。施加生理流量和标准边界条件。通过分析动脉瘤内的速度、涡度和剪切率大小以及动脉瘤表面的壁面剪切应力 (WSS)，对两种方法进行比较。还计算了没有装置的模拟。对于剪切和惯性驱动流动模型，平均流量减少分别达到 76%和 41%。当比较两种方法时，结果表明流动模式和大小非常相似。WSS、等速度面和横截面平面上的速度非常吻合。研究参数的均方根误差在动脉瘤速度上达到 20%，在动脉瘤剪切率上达到 30.6%，在动脉瘤涡度上达到 47.4%。在动脉瘤表面计算的 WSS 上达到 20.6%。该方法的优点在于其易于实现和计算时间的节省。多孔介质方法预测的结果与真实支架几何模型很好地吻合，可以预测装置对动脉瘤内流动的主要影响，从而便于分析。
