| Vascular obstructive diseases induced by atherosclerosis are a severe threat to mankind's health and security, to which vascular stenting is an extensive treatment with rapid development. However, in-stent restenosis (ISR) may occur after stenting, which mainly affects the clinical results even though drug eluting stents can reduce ISR rates to a certain degree. Properties and design of stents are regarded as a key factor influencing ISR, which are difficult to study using conventional method for stents' tiny dimension, complicated structure, and expensive prototyping and testing. So finite element analysis and optimization method play an important role in stent research and design works. This paper aims at several new research subjects of stent properties and designs. Finite element analysis code ANSYS and optimization software OptiStruct are applied to build stent property analyzing and design optimizing models.Based on "volume controlled" balloon model, stent-balloon model is built to study stent expansion properties. Three models are built to study stent bending deformation properties: Stent flexibility model using multipoint constraint elements; stent cell and strut distribution model based on rigid vessel model; and stent-curved vessel interaction model. Delivery and release model of carotid stent is built to study interactions between self-expandable TiNi stent and bifurcated vessel. Topology optimization model is built to optimize structure of drug eluting stent platform with reservoirs on struts. Pure iron stent implanting model is built to study mechanical behavior of metal biodegradable stents. The simulations show that:Stent-balloon expansion model can result in accurate expansion deformation parameters, simulate complete expansion procedure and follow the highly nonlinear relation between balloon pressure and stent diameter.Stent flexibility model can apply four-point bending test to three-dimensional stent models and simulate complex stent bending. Stent cell and strut distribution model compared the bending deformation of the Express and Nirflex stent model. With bending deformation, a stent should deform as a whole to reduce the severe vessel prolapse; and the adjacent bows should avoid "peak-peak" design but have "peak-valley" design to reduce the strut contact and overlapping. When a stent is implanted in a curved vessel, the outer curvature of vessel has hinge points at stent edges, which results in stress concentration; the inner curvature of vessel depart from stent edges, which adversely influences the hemo-dynamics and drug function of drug eluting stents. The stent design for curved vessels should consider more flexible edges.Material model of shape memory alloy provided by ANSYS can simulate superelastic behavior of TiNi. Superelastic carotid stent model can be delivered and released in bifurcated vessel model through rigid catheter model. The stent with shorter strut design can improve conformability and scaffolding.The single strut stiffness is increased by 14% for drug eluting stent platform with reservoirs using topology optimization, and the drug holding capacity was retained as the original design. Manufacturing constraint is critical to result in simple and clear element mesh distribution and the OSSmooth function of OptiStruct will provide great convenience to design concept.The design of strut thickness and width of biodegradable stent has great effects on scaffolding, stent stress and strain, and tissue stress. Compared with stainless steel stent having the same configuration, biodegradable pure iron stents have lower scaffolding but greatly reduce tissue stress for stent implanting.These finite element analyzing and optimizing models provide numerical models and novel optimal designs for some new subjects occurred in stent research and development. These results will help stent designers devise more outstanding stent to reduce ISR rates, and contribute to stent technology development and treatment of vascular obstructive diseases.
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