Abstract
We have been developing a micro porous covered stent as a newly device for cerebral aneurysm treatment to adapt large and giant cerebral aneurysm with a broad neck. This stent has a porous film to control among thrombus formation, rapid neointimal formation and intimal hyperplasia. It is expected that the neointimal formation becomes earlier by using much larger pores. But there is a possibility that the covered stent with large pare cannot embolize an aneurysm by increasing inflow from parent vessel. The purpose of this study is optimization of pore design to ensure compatibility between reliable embolization and controlling early neointimal formation, in-vitro experiment based on flow similarity low has been conducted by using a 2D parent vessel model with a side wall type aneurysm model. The flow visualization result shows that three kinds of flow pattern in the aneurysm were observed namely, viscous shear induced flow, pressure drop induced flow and those coexistence flow. According to PIV measurement result, area mean shear rate in the aneurysm after stenting was decreased to less than 1/5 of before stenting. Especially, when the covered stents of which aperture diameter was lower than 200μm and aperture ratio was 60% were installed, shear rate in aneurysm was less than 1 s^<-1> which was a threshold of F-IX activating necessary for venous thrombus formation.
