發(fā)布時間：2018-05-14 10:22

  本文選題：形狀記憶合金 + 可降解聚合物�。� 參考：《上海交通大學》2013年碩士論文

【摘要】：心血管疾病是人類的第一大殺手，而血管支架置入術是目前針對這一疾病最為有效的治療手段，但限制這一治療技術的主要原因是支架內(nèi)再狹窄：即由于血管在支架植入后的過度增生而造成血管內(nèi)部管腔再次狹窄。盡管影響支架內(nèi)再狹窄的因素有很多，如支架結構、患者的個體差異、是否患有糖尿病、以及是否具有吸煙習慣等，但其主要成因之一即為在血管支架在植入過程中球囊快速擴張而造成的血管壁的撕裂損傷而引起的后續(xù)免疫反應，以及平滑肌過度遷移增殖反應。因此，如果能夠在支架置入過程中甚至置入后，盡量減少支架擴張對于周圍血管組織的刺激及損傷是降低血管支架內(nèi)再狹窄的有效手段。 在漸進擴張式血管支架設計過程中，如何實現(xiàn)漸進擴張原理，同時又不過多的增加支架結構的復雜程度是設計的關鍵所在。本研究中提出了基于形狀記憶合金和可降解聚合物的漸進擴張式血管支架設計。由于形狀記憶合金超彈性特性使其可以滿足作為支架材料可以承受較大應變量這一要求。同時，經(jīng)過變形后的形狀記憶合金在置入后會由于其內(nèi)部存儲的變形能，逐漸向外擴張以進一步恢復其原有形狀。在復合了由可降解聚合物制成的支架限制單元后，支架的擴張速度不僅取決于其壓握程度，還受到限制單元的限制。通過調(diào)節(jié)支架擴張力和限制單元的限制作用以使的支架能夠在血管壁可以接受的速度漸進擴張。 本文首先通過實驗的方法測定了形狀記憶合金和可降解聚合物的材料特性。其中，形狀記憶合金的材料參數(shù)通過單軸拉伸的方式獲得，并采用靜態(tài)降解的方式，對可降解聚合物在靜態(tài)降解過程中的材料特性進行了初步的研究。實驗發(fā)現(xiàn)，可降解聚合物在靜態(tài)降解過程中，其彈性模量基本無變化，，但延展率隨著降解時間的推移逐漸變小，即隨著降解時間的推移材料逐漸變脆、變硬。 文中進一步探討了基于兩種不同結構的自擴張鎳鈦合金支架的漸擴張式血管支架設計方案，討論了在不同情況下血管支架漸進擴張的實現(xiàn)方式及各自的優(yōu)缺點，并最終選擇圓管切割型設計方案。同時，通過對鎳鈦合金的熱處理，采用放大的支架單元的形式對漸擴張支架的設計原理進行了相應的驗證。進而，為了更為方便的對支架的擴張狀態(tài)及結果進行相應的調(diào)整，利用有限元方法建立了包含支架從最初的設計過程到體內(nèi)置入的模擬過程。數(shù)值模擬結果表明，支架的初期擴張量可以很方便的通過改變限制單元的長度和厚度進行調(diào)節(jié)和控制。
[Abstract]:Cardiovascular disease is the first killer of human beings, and stent implantation is the most effective treatment for this disease. However, the main reason for limiting this treatment technique is stent restenosis, that is, the re-stenosis of intravascular lumen due to excessive proliferation of blood vessels after stent implantation. Although there are many factors affecting restenosis in stents, such as stenting structure, individual differences in patients, diabetes mellitus, and smoking habits, etc. However, one of the main causes is the subsequent immune response caused by the rapid balloon dilation of vascular stents and the proliferation of smooth muscle. Therefore, it is an effective way to reduce the restenosis of stent by minimizing the stimulation and injury of stent dilatation to the surrounding vascular tissue, if the stent can be inserted during or even after implantation. How to realize the principle of progressive expansion while not increasing the complexity of stent structure is the key to the design of progressive dilation stent. In this study, a progressive dilatation stent design based on shape memory alloy and degradable polymer was proposed. Because of the superelastic properties of shape memory alloy, it can be used as scaffold material to withstand large strain. At the same time, the shape memory alloy after deformation will gradually expand outward to further restore its original shape because of the deformation energy stored inside. The expansion speed of the scaffold is not only dependent on its grip degree, but also limited by the limiting unit after recombination of the scaffold which is made of degradable polymer. By adjusting the dilatation force and limiting effect of the limiting unit, the stent can expand gradually at an acceptable rate on the vascular wall. In this paper, the properties of shape memory alloys and degradable polymers were measured experimentally. Among them, the material parameters of shape memory alloy were obtained by uniaxial tensile method, and the properties of degradable polymers in the static degradation process were studied by static degradation method. It was found that the elastic modulus of degradable polymers remained unchanged in the static degradation process, but the elongation rate decreased with the degradation time, that is, the materials became brittle and hardened with the degradation time. In this paper, we further discuss the design scheme of gradually expanding vascular stent based on two different structures of self-expanding Ni-Ti alloy stent, and discuss the realization of progressive dilatation of vascular stent under different conditions and their respective advantages and disadvantages. And the final choice of circular pipe cutting design. At the same time, the design principle of the expanding stent was verified by the heat treatment of Ni Ti alloy and the form of enlarged support unit. Furthermore, in order to adjust the expansion state and the results of the scaffold more conveniently, the simulation process including the initial design process and the internal placement of the scaffold was established by using the finite element method. Numerical simulation results show that the initial expansion of the support can be easily adjusted and controlled by changing the length and thickness of the limiting unit.
【學位授予單位】：上海交通大學
【學位級別】：碩士
【學位授予年份】：2013
【分類號】：R318.11

【參考文獻】

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本文編號：1887481