Development of asymmetric stent designs, and, Validation through finite element analysis simulations
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Ruptured aneurysms are one of the major contributors of cerebral stroke and hence lead to over 500,000 deaths in the United States each year. Treatment of diagnosed aneurysms is vital in prevention of stroke and is a principal motivation for ongoing research in this field. The primary modes of treating a diagnosed aneurysm are endovascular coiling and surgical clipping. Surgical clipping remains an invasive technique while endovascular coiling is ineffective in treating wide-neck and fusiform aneurysms. A new minimally invasive technique to treat the aneurysms by using an "Asymmetric Stent" was developed by our lab, Toshiba Stroke Research Center, and tested successfully. These asymmetric stents are made by laser-welding a low-porosity metallic patch onto stainless steel coronary stent. Present thesis introduces new techniques for designing an improved version of these asymmetric stents using Computer Aided Design tools. These new designs integrate the asymmetric patch with the rest of the stent structure, thereby eliminating the welding process. These designs also serve as a basis for creation of future novel symmetric as well asymmetric stent designs. Also presented in this thesis, are validation techniques for these stent designs through Finite Element Analysis simulations. A new method is formulated for realistically representing the crimping behavior of the symmetric stent using displacement loading. This method fares significantly better than the previously developed techniques. Potential of this technique, as a basis for simulating the entire lifecycle of stent, is also investigated.