Development of microporous covered stent for cerebral aneurysm treatment (hydrodynamical evaluation of stent embolization and optimization of pore design of microporous film)

Abstract

The authors have been developing a microporous covered stent as a newly device for cerebral aneurysm treatment. This stent has a porous film to control both embolization and rapid neointimal formation. According to previous study, 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 by increasing inflow from the parent vessel. The purpose of this study is estimation of stent embolization and optimization of pore design to ensure compatibility between reliable embolization and controlling early neointimal formation, in-vitro experiment under the steady flow condition based on flow similarity law has been conducted by using a two dimensional parent vessel model with a saccular aneurysm model and simplified micro-porous film models. The PIV results show that mean shear rate in the aneurysm model after stenting, of which pore diameter is <300μm and porosity is 60%, was decreased to less than 1/10 of before stenting. According to flow visualization, it is considered that viscous shear force caused by shear flow in the vicinity of the parent vessel wall drives the blood in the aneurysm cavity passing through the micro-pores on the film. As the result of the driving force estimating, it is suggested that ratio of the viscous shear force to rotational moment of the blood in the aneurysm cavity is one of the important hydrodynamical parameter to estimate the flow pattern in aneurysm and the stent embolization. © 2013 The Japan Society of Mechanical Engineers.