Applications of Finite Element Analysis: Computational Studies of Angioplasty Balloon and Sac

現今心血管疾病在開發國家中已成為主要的死亡因素，國人十大死因報告中心臟疾病也高居第二位，是現代人不容忽視的疾病之一。本研究利用ABAQUS建立數個心血管疾病相關的有限元素模型，共分為三個部分：第一部分發展一理想冠狀動脈部署模型，並與先前的研究比較有無氣球在部署模型結果的差異，由結果可看出本研究所建立的冠狀動脈部署模型中，氣球會先將血管支架撐成一類似狗骨頭的形狀，再提供足夠的徑向力撐開血管，與臨床上所得的結果較接近；第二部分為一新型左心室輔助器的分析，模擬心室輔助器中的氣囊置於人體中承受週期性負載的情形，並探討氣囊不同的幾何設計參數的影響。模擬結果顯示，氣囊的厚度為影響安全係數及可承受的壓力差最主要的因素，然而考量其需置於人體內承受反覆的收縮及舒張負載，厚度0.275mm為一較佳的選擇。在葉片幾何設計的部分，本研究比較了不同厚度與長度設計參數的葉片之分析結果，葉片的長度變化會影響氣球與葉片交界處之應力、應變集中現象，相較之下，葉片的厚度漸縮變化所造成的影響則幾乎可忽略；第三部分則是一以Simultaneous Kissing Stenting（SKS）治療策略為例的分叉病變分析模型，利用VDISP子程序大幅降低兩血管支架推送至病變處所需的分析時間，並以準靜態分析模擬兩血管支架於與氣球、分叉病變間複雜的交互作問題。 有別於一般實驗以及臨床情況容易受到外界環境因素干擾而影響實驗結果，有限元素分析可確保獨立單一變數來進行實驗分析，並針對該變數所造成的臨床影響進行研究並加以改善。本研究所建立的有限元素分析模型提供了在工程角度上及臨床上的評估，其結果可作為未來醫療器材設計的考量，亦可用於術前分析，提供醫師與相關醫療人員更完整的資訊及手術風險評估，提升整體的醫療成效。Cardiovascular disease is now the leading cause of death worldwide. To investigate cardiovascular-related diseases, finite element models were developed in this study. The study is organized as follows: In the first part, a finite element model is established to investigate stent-artery interaction with absence of a realistic balloon. A comparison of previous study is shown that the balloon and the stent expand in a non-uniform end-first manner (the dogbonning effect), and then apply radial force to enlarge the arterial wall. A numerical analysis of novel left ventricular assist device is developed to evaluate the mechanical integrity and pulsatile fatigue resistance of the blood sac in the second part. The results show that the sac thickness is the key factor for safety factor and 0.275 mm is a better choice for resistance of periodic physiologic loading. The length and thickness of lobes are also investigated whether it reduce the stress/strain concentration near the connection region of lobes and sac. The results show that lobe length may affect the stress/strain concentration while tapered lobe thickness causes almost negligible results. In the last part, a bifurcation intervention strategy model of simultaneous kissing stenting technique (SKS) is developed while VDISP user subroutine is used to simulate the interaction behavior between two balloon-expandable stents, balloon and bifurcation lesions. Computational modeling has become a prevalent tool due to its ability to investigate the influence of individual parameters and improve the temporal efficiency of new product development. Finite element models developed in this study could give insights into various aspects of future design optimization for new biomaterials or biomedical devices. It is also feasible to provide a guideline for physicians and medical personnels to achieve the best clinical outcome