- 學位論文
圓截面中空支柱之新型血管支架
New Stent Design with Round and Hollow Stent Struts
摘要
微型儲藥槽血管支架為未來植入式醫療器材之流行新趨勢，不僅可以作為傳統塗藥血管支架之另一選項，也能應用於治療癌症之新藥物載具，除了大幅減低血管支架的尺寸之外，亦包含增加攜帶藥物之劑量、於不同時間點釋放不同藥物、同時攜帶多種藥物並治療兩種以上疾病等可能。然而，血管支架進行微型儲藥槽之加工時將會弱化血管支架的機械性質，例如：徑向力強度、疲勞安全係數等。 由於部分血管之內徑相當狹窄，或是阻塞區域造成血管內徑相當狹隘，使得血管支架難以通行，造成醫師在輸送上有一定的困難度，因此便有了截面為圓形之血管支架的概念，可提升血管支架之追蹤性 (Trackability) 與通過性 (Crossability)，有助於醫師解決於小血管患者中經常遇到的問題。 本研究結合微型儲藥槽與圓截面血管支架之概念，提出一項新穎的設計概念，即為圓截面中空支柱血管支架，以空心結構取代原本的實心結構，使實心結構血管支架變成由中空支柱組合而成的血管支架，除了可將藥物儲存於中空的部分，藉此提升血管支架的儲藥量，亦能克服方截面血管支架難以遞送的問題。並以有限元素軟體建立血管支架之徑向支撐強度測試模型與疲勞測試模型，以Goodman疲勞安全壽命分析法計算疲勞安全係數。從電腦模擬的結果顯示，當血管支架的厚度為血管支架半徑的60%時，相較於圓截面塗藥血管支架，圓截面中空支柱血管支架之徑向支撐強度與疲勞安全係數僅降低了12.2%與12.7%，而儲藥量提升了3倍。與圓截面微型儲藥槽血管支架相比，圓截面中空支柱血管支架之徑向支撐強度僅有3.6%的降幅，疲勞安全係數與儲藥量則提升了2.3%與2倍。本研究之設計概念能有效平衡各項機械性質，並提高血管支架之儲藥量，提供新一代血管支架作為設計參考。
並列摘要
In recent years, an innovative variation of the drug-eluting stent with micro-sized drug reservoirs (depot stent) has been introduced. It is not only an alternative of conventional drug-eluting stents but a potential drug carrier treating for various diseases such as cancer. Depot stents take advantages in many ways including programmable drug delivery with both spatial and temporal control and higher drug capacity. However, creating such reservoirs on the stent may weaken the structure of the stent and compromise its mechanical integrity such as radial strength and fatigue safety factor. Stents deployment could sometimes face difficulties when the lumen is too narrowed or completely blocked. Therefore, an innovative variation of stent with round struts has been introduced. It increases the trackability and crossability of stents to overcome these problems. In this study, a novel stent design with round and hollow stent struts was proposed. The concept of this design is to replace the solid struts with the hollow struts to increase drug capacity and deliverability at the same time. Finite element models and Goodman life analysis were developed to evaluate the mechanical integrity and pulsatile fatigue resistance of the stent to various loading conditions. Simulation results show that the optimized design exists when stent thickness is 60% of the stent radius. The total drug capacity of the proposed stent with round and hollow struts could be increased by 3 times with a minimum tradeoff in its radial strength and fatigue life (-12.2% and -12.7%) comparing with the drug-eluting stent with round struts. In addition, the total drug capacity of the proposed stent could be increased by 2 times without any tradeoff in its fatigue life when it compares to the depot stent with round struts. Therefore, the proposed stent could carry more drugs with a few compromises than its drug-eluting stent counterparts, thereby opening up a wide variety of new treatment potentials and guidelines of stent design.