Research on Optimum Design of Stent Used for Interventional Treatment Apparatus of Aneurysms

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For the purpose of optimum design of stent used for the treatment of aneurysms, numerical simulations were performed to obtain the design criterion. Saccular aneurysm was chose as a model aneurysm and stent was located in the parent artery at the neck of the aneurysm. Then, the speed of blood flow in the aneurysm decreases and it is expected that thrombus generates on the inner wall of aneurysm, resulting in hardening of the aneurysm wall and prevention of aneurysm growth and rupture. The following results were obtained from the calculation results. (1)When the flow becomes maximum in the aneurysm, it enters the aneurysm from upstream side of the aneurysm neck, flows along the inner wall of the aneurysm, and discharges from downstream side of aneurysm neck. (2)The pressure in the aneurysm becomes almost uniform, but the pressure pulsates with time having average the value of upstream and downstream sides of the aneurysm. (3)The driving forces of flow in the aneurysm is pressure differe … More nce between upstream and downstream sides in the aneurysm and momentum of flow in the boundary layer of the parent artery which impinges on the stent filaments and then deflects from axial to radial direction. (4)The generation of the thrombus can be judged based on the wall shear rate of the blood flow. In order to check the effectiveness of the placement of the stent, flow measurement near the stent filaments and in the aneurysm is necessary. We have developed cathetertype LDV-sensor having 100μ m in outer diameter for measuring the local blood flow velocity in blood vessels. By inserting this sensor across the stent into the aneurysm, it is possible to measure the local flow velocity in the aneurysm. Numerical simulation of flow around this sensor was performed to estimate measurement error due to the existence of the sensor in the flow field which is to be measured. Furthermore, it is known that the blood viscosity increases in the region where the flow velocity is low. This is due to non-Newtonian rheological behavior of the blood in the low flow region. Therefore, in order to estimate the effect of the stent with high accuracy, accurate modeling of the rheology of blood flow is necessary by solving the coupled problem between the deformation of the red blood cell and plasma flow around it. A coupled analysis by using immersed boundary method was proposed and the effectiveness of the method was confirmed by numerical simulations. Less