血栓取出器之設計與體外實驗驗證

Abstract

急性缺血性腦中風的成因為腦血管受急性血栓阻塞而影響血流，導致患者殘障或死亡。近年來，針對急性血栓的治療，機械取栓方法逐漸普及，其中一種機械取栓的治療方法為鎳鈦合金自動擴張式支架所構成的血栓取出器。目前市面上已經有數款血栓取出器產品，但難以明確指出不同的幾何形狀設計及其機械性質對於取栓效果的影響，本研究將針對血栓取出器設計對取栓效果的影響進行研究。 本研究藉由參數化設計定義血栓取出器的幾何結構，以設計參數crown數與ring數作為控制變因提出6款設計。建立有限元素模型觀察機械性質並確認製造可行性後，便能進行雛型品製造。最後由體外取栓實驗驗證血栓取出器雛型品的取栓效果，分別於直管血管、彎管血管進行5次定量實驗以及25次定性實驗，並與有限元素分析結果進行比較。 結果顯示，有效工作長度、幾何形狀表面起伏與徑向強度對取栓效果的影響皆不明顯。在直管血管實驗中，設計參數ring數影響血栓斷裂或血栓脫落的發生，而對血管壁的貼合程度則影響血栓碎屑與液體殘留的出現；在彎管血管方面，血栓取出器於彎曲處的展開程度是主要影響血栓斷裂與血栓脫落的因素。透過本研究建立的血栓取出器系統性研究方法，成功找到設計參數對取栓效果的影響，希望能提供血栓取出器新的開發方向。

Acute ischemic stroke, usually caused by sudden blood clot formation, could lead to fatal blockage in arteries with high mortality and morbidity. In recent times the mechanical thrombectomy devices have become increasingly involved in blood clot removal. The blood clot retriever, one kind of thrombectomy devices, is a nitinol self-expanding stent used to retrieve the blood clot. Currently, there are several kinds of blood clot retriever products on the market, but the designs of blood clot retrievers are not studied systematically. This research aims to evaluate the performance of blood clot retriever designs. In this research, parametric design methodology was used in device design. Crown number and ring number, two of the design parameters, were treated as control variables and achieved six blood clot retriever design patterns. Finite element models were developed to analyze the mechanical behavior and the manufacturing feasibility of the devices. Then, the prototypes of blood clot retrievers would be produced. Finally, the in-vitro experiments were conducted to verify the effectiveness of these blood clot retrievers. Twenty-five quantitative experiments and five qualitative experiments were conducted with six blood clot retrievers in each of straight vessel and tortuous vessel. The in-vitro experiments results would be compared with finite element analysis results. Results show that the effects of working length, radial stiffness, and deformation on effectiveness of blood clot retrievers are not obvious. In the straight vessel experiment, the ring number of design parameters affects the occurrence of clot disengagement and fragmentation, and the malapposition of blood clot retriever affects micro-fragmentation and blood residue. In the tortuous vessel experiment, the conformability of blood clot retriever is the crucial factor of effectiveness. In this research, a systematic study method for blood clot retriever was proposed, and the relationship between design parameters and effectiveness of blood clot retrievers were established. It is hoped that this research could provide a new direction for blood clot retriever development.