Design and Shape Optimization of a Biodegradable Polymeric Stent for Curved Arteries Using FEM

Abstract

Stent treatment has revealed safe and efficient outcomes for straight arteries, while it is still challenging for curved coronary arteries. On the one hand, a stent should be flexible enough to take the artery’s curvature with the least stress to the artery wall. On the other hand, it has to be strong enough to prevent any artery diameter reduction after the implant. In this work, the genetic algorithm multi-objective optimization method is exploited to provide a Pareto set and to design a curvature stent. The design has been performed based on the appropriate flexibility and radial strength design, depending on the characteristics of a particular case study. In the optimization procedure, flexibility and radial strength have been evaluated based on ASTM standard mechanical tests. These tests have been parametrically simulated using the finite element method. The strut curvature is formed by the spline curvature, whose middle point coordinates are two of the optimization variables. The other optimization variable is the thickness of the stent. Based on the Pareto set achieved from the optimization, five different stent designs have been proposed. In these designs, the middle part of the stent is stiffer (in the plaque aggregated) and benefits more radial strength rather than flexibility. At the stent’s extremes, where more deformation takes place, flexibility is weighted more than radial strength. These five design sets differ in their objective weight ratios. At the end of this research, their implementation in a curved vessel is simulated in ABAQUS/CAE, and von Mises stress distribution, maximum von Mises stress, and stent recoil after imposing the stent have been analyzed. The obtained Pareto front can also be a useful guide for physicians to design and manufacture customized stents for each patient.