可降解聚合物血管支架结构优化设计

OPTIMIZATION DESIGN OF DEGRADABLE POLYMER VASCULAR STENT STRUCTURE

聚合物血管支架由于材料刚度较低导致其径向支撑能力相对于金属血管支架较弱,通常采用增大支架筋宽和厚度的方式来提高其径向支撑能力,但这不仅会降低支架的柔顺性能,减小血管管腔获得面积,还会增大表面覆盖率,从而增大支架内再狭窄的风险.为了设计出具有较小筋宽和厚度的聚合物血管支架,提高其径向支撑能力,本文采用一种将Kriging代理模型和有限元方法相结合的优化方法来优化支架的结构.采用Kriging代理模型建立设计目标和设计变量之间近似的函数关系,采用优化拉丁超立方抽样方法选取初始样本点,采用EI函数平衡局部和全局搜索,以便获得全局最优解.选取ART18Z聚合物支架作为算例,首先将支架的筋宽和厚度各减小0.02 mm,然后采用优化方法优化ART18Z支架的几何结构参数.数值结果表明,优化后ART18Z支架的综合服役性能得到改善,文中提出的优化方法能有效地应用于聚合物血管支架的优化设计.

Due to the low sti_ness of polymers,polymeric stent has lower radial support capability compared to metallic stent.Therefore,the width and thickness of the stent are usually increased to improve its radial support capability,which can not only reduce the flexible performance of the stent and the area of the vascular lumen,but also increase the surface coverage and thus increase the risk of in-stent restenosis.In order to design polymeric stent with smaller strut width and thickness and improve its radial support capability,an optimization method combining with Kriging surrogate model and finite element method was used to optimize the geometries of stent.Kriging surrogate model was used to construct the approximate function relationship between design objectives and design variables.Optimized Latin Hypercube Sampling method was used to select the initial sample points.EI function was used to balance global and local search and tend to find the global optimal solution.As an example,ART18Z polymeric stent was studied in this paper.Firstly,the strut width and thickness of the stent were respectively reduced by0.02mm,and then the optimization method was used to optimize the key geometric parameters of ART18Z stent.The numerical results show that the overall service performance of ART18Z stent was improved after optimization and the proposed optimization method can be effectively applied to the optimal design of the polymeric stent.