Development of fluid-structure interaction simulator and its evaluation by in vitro measurement

我们开发了一个集成的心血管系统模拟器，并对人大脑中动脉动脉瘤（MCAA）进行了基于图像的建模和流固耦合（FSI）有限元分析（FEA）。基于CT图像构建MCAA的计算模型。1)心血管系统模拟器的开发假设流体是层流的、牛顿的、粘性的、不可压缩的来代表血液。假定动脉壁是超弹性的、各向同性的、不可压缩的和均匀的。流固耦合采用强耦合方法。模拟结果表明，血流对脑动脉瘤壁面的水动力不小，为了准确分析脑动脉瘤，需要进行FSI分析。我们还基于解剖学知识构建了外周血管网络，并将考虑外周血管网络影响的边界条件应用于三维血流动力学模拟。周围血管的一维分析是三维分析的边界条件，二维模型是一维分析的边界条件。0D模型采用结构树阻抗模型。采用1D分析和0D模型对血管周边电阻、柔度和阻抗进行了分析。结果表明，本方法在各动脉流速上有显著差异，血流分布和流向得到改善。特别是在闭塞的情况下，可以观察到Willis动脉圈的侧支血流。2)体外模型与真实血管几何的实验采用快速成型系统和丢失模型技术制作体外模型。该模型具有真实的血管几何形状，在脑动脉瘤分叉区。动脉瘤内流动结构的测量是在稳定流入条件下进行的。根据流速数据计算流线，并观察沿动脉瘤壁面的流动结构。利用速度数据和几何数据计算壁面剪切应力（WSS），在动脉瘤内观察到高WSS区域。3)数值分析与实验结果的比较采用相同条件下体外模型血管几何形状，将实验结果与数值分析结果进行比较。流速分布和流线型相似，但不同区域出现高WSS。少

We developed an integrated cardiovascular system simulator and conducted image-based modeling and Fluid-Structure Interaction (FSI) Finite Element analysis (FEA) of human middle cerebral arterial aneurysm (MCAA). The computational model of MCAA is constructed from CT images.1)Development of cardiovascular system simulatorThe fluid is assumed to be laminar, Newtonian, viscous, and incompressible to represent blood. The arterial wall is assumed to be hyperelastic, isotropic, incompressible, and homogeneous. Fluid-structure coupling is performed by strong coupling method.The simulation result suggests that the hydrodynamic force of blood flow on aneurysm wall is not small and FSI analysis should be conducted for accurate analysis of cerebral aneurysm.We also structured peripheral vessel network based on anatomical knowledge, and applied the boundary condition taking account of the effects of peripheral vessel network to 3D hemodynamic simulation. 1D analysis of the peripheral vessels is a … More pplied as the boundary condition for 3D analysis, and 0D model as that for 1D analysis. For 0D model, structured tree impedance model is employed. The peripheral resistance, compliance, and impedance of vessel are treated by 1D analysis and 0D model.As a result, the present method shows a significant difference in flow rate of each artery and improvement in flow distribution and direction. Particularly, for the case with occlusion, collateral flow in the arterial circle of Willis is observed.2)Experiment using in vitro model with realistic vessel geometryWe made the in vitro model using rapid prototyping system and lost model technique. The model has realistic vessel geometry with cerebral aneurysm at bifurcation area. The measurement of flow structure in the aneurysm was conducted under the steady inflow conditions. The streamline is calculated form velocity data, and the flow structure along the aneurysm wall was observed. As the result of calculating the WSS (wall shear stress) using velocity data and geometry data, high WSS area was observed in the aneurysm.3) Comparison between numerical analysis and experimental resultWe compared experimental result to numerical analysis using the vessel geometry of in vitro model at same conditions. The velocity distribution and streamline pattern were similar, but high WSS was appeared at different area. Less