Development of Measuring System for In Vitro Hemodynamics and Evaluation of Fluid Forces Acting on Blood Vessel Walls

本研究有两个主要目的。第一个是开发一种测量系统，用于测量作用在血管壁上的流体力（即压力和剪切应力），从而测量这些流体力的脉动特性。二是利用开发的系统，利用真实患者的MRI数据制作动脉瘤模型，通过体外实验来评估这种流体力。另一个目的是利用MRI数据进行三维流体流动计算，以获得实验中无法获得的流体动力学量信息。结果如下：(1)利用真实患者的MRI数据制作脑动脉瘤硅橡胶模型，进行基于指标匹配技术的立体PIV测量。在三种稳定速度条件下，测量了两种动脉瘤模型（破裂模型和未破裂模型）在多个截面上的三分量平均速度分布。(2)从测量的三分量速度分布中评估作用在动脉瘤壁上的壁面剪应力的方法。特别注意了壁面附近速度的插值方法。(3)将该方法应用于立体PIV测量数据。计算了墙体的剪应力，并分析了墙体位置不确定性的影响。(4)研究了一种利用MRI模型导出数据进行脑动脉瘤内流体流动三维计算的方法。利用市售CFD代码，确定了适合脑动脉瘤血流动力学的入口和出口条件。(5)采用CFD方法对破裂模型、未破裂模型和待破裂模型三种不同的动脉瘤模型进行了稳态和脉动流体流动研究。从计算结果中明确了速度分布、壁面压力分布和壁面剪应力分布。

The present study has two main objectives. The first one is to develop a measuring system for fluid forces (i.e., pressure and shear stresses) acting on blood vessel walls and thus for pulsating characteristics of those fluid forces. The second one is to evaluate, by using the system developed, such fluid forces through in vitro experiment using aneurysm models made from MRI data taken from real patients. An additional objective is to conduct 3-D fluid flow computations using the MRI data in order to obtain information of fluid dynamic quantities unavailable from experiment The outcomes are as follows:(1) Stereo PIV measurements based on the index-matching technique are carried out by using silicone-rubber models of cerebral aneurysm made from MRI data taken from real patients. Distributions of three-component mean velocities in multiple cross-sections in two aneurysm models, a ruptured model and an unruptured model, are measured at three steady velocity conditions.(2) A method for evaluating, from three-component velocity distributions measured, the wall shear stresses acting on the aneurysm walls. Particular attention is paid to the interpolation scheme for velocities near the wall.(3) The method is applied to the data taken in the stereo PIV measurements. The wall shear stresses are evaluated and the effect of the uncertainties in the wall position is examined.(4) A method for 3-D computations for fluid flows in cerebral aneurysms using exported data from MRI models is studied. A commercially available CFD code is utilized and the inlet and outlet conditions appropriate from hemodynamics in cerebral aneurysm are determined.(5) The CFD method is used to investigate both steady and pulsatile fluid flows in three different aneurysm models, a ruptured model, an unruptured model and a to-be-ruptured model. Velocity distributions, wall pressure distributions and wall shear stress distributions are clarified from the computed results.