本文選題：血管支架 + 膨脹性�。� 參考：《大連理工大學(xué)》2011年博士論文

【摘要】：心血管病是威脅居民健康的重大疾病。據(jù)統(tǒng)計(jì),國內(nèi)每年死于心血管病的人數(shù)約為三百萬,占總死亡人數(shù)的45%左右,每年用于心血管病的醫(yī)療費(fèi)用超過1300億元人民幣。冠狀動脈內(nèi)支架植入術(shù)是治療冠心病的一種有效手段,近年來越來越多地得到了廣泛應(yīng)用。冠脈支架的力學(xué)性能,是關(guān)系到支架術(shù)效果的關(guān)鍵因素之一。許多醫(yī)務(wù)工作者和工程界的學(xué)者都在努力研究這一課題。本文利用有限元方法來研究冠脈支架的力學(xué)性能。 論文的主要工作包括： 針對冠脈裸支架結(jié)構(gòu),研究了有限元模型所采用的單元類型(高階實(shí)體單元、低階實(shí)體單元、殼單元、梁單元)和網(wǎng)格剖分密度對計(jì)算效率和精度的影響,模擬了冠脈裸支架全壽命內(nèi)的變形過程所涉及到的力學(xué)性能。通過模擬支架生產(chǎn)過程中的壓握變形、手術(shù)過程中的膨脹變形以及在冠狀動脈內(nèi)長期工作時的壓縮變形,本文發(fā)現(xiàn)：壓握過程對膨脹性能的影響較小,而膨脹程度對支架在工作狀態(tài)下抵抗壓縮載荷的徑向支撐力具有較大的影響。另外,根據(jù)支架的膨脹性能曲線進(jìn)行深入分析后得到了膨脹速度曲線,發(fā)現(xiàn)了膨脹速度曲線與支架的最佳膨脹范圍的內(nèi)在聯(lián)系。 本文對冠脈支架與球囊的接觸問題進(jìn)行了模擬,得到了比較準(zhǔn)確的變形結(jié)果。在此基礎(chǔ)上,提出了利用應(yīng)變能來計(jì)算真實(shí)接觸壓力的方法。一般來說,通過接觸分析所得到的球囊與支架間的接觸壓力,與實(shí)際情況下均勻一致的壓力相比,誤差往往比較大,這是由于支架金屬絲比較細(xì)而只能在接觸面上采用較粗的網(wǎng)格單元所導(dǎo)致的。根據(jù)功能原理,并且考慮到接觸壓力是驅(qū)動支架膨脹而產(chǎn)生應(yīng)變能的唯一直接原因,本文利用支架應(yīng)變能占全部應(yīng)變能的百分比對膨脹載荷進(jìn)行了修正,得到了支架與球囊之間真實(shí)而且均勻的接觸壓力,其結(jié)果與裸支架的膨脹曲線相互一致。這個方法可以作為驗(yàn)證接觸分析結(jié)果正確性的依據(jù)。 針對冠脈支架的縱向柔順性,建立的懸臂梁彎曲模型,克服了三點(diǎn)載荷法和簡支梁模型的缺陷,能夠更準(zhǔn)確、更全面地描述支架整體彎曲性能。以該模型為基礎(chǔ),本文詳細(xì)研究了目標(biāo)支架在較大彎曲曲率范圍內(nèi)的瞬時抗彎剛度情況,結(jié)果表明：在彎曲曲率較小的情況下,支架瞬時抗彎剛度一般表現(xiàn)為各向同性；而當(dāng)彎曲曲率較大時,則出現(xiàn)非常明顯的各向異性。此外,利用懸臂梁模型還發(fā)現(xiàn),支架彎曲時還伴隨發(fā)生了在彎曲平面外的側(cè)向偏轉(zhuǎn)以及繞支架中心軸的扭轉(zhuǎn)變形。這兩種附帶變形是由支架彎曲變形而引起的,在一定程度上改變了支架的實(shí)際彎曲方向和曲率。這兩種附帶變形也正是瞬時彎曲剛度存在各向異性的證據(jù)。 在優(yōu)化設(shè)計(jì)工作中,利用ANSYS的APDL語言開發(fā)了適用于冠脈血管支架有限元分析的計(jì)算程序,該程序具有自動化運(yùn)行、參數(shù)化建模、仝過程分析、魯棒性計(jì)算及優(yōu)化等特點(diǎn),將此程序進(jìn)一步加以完善后,即可作為專門用于血管支架力學(xué)性能模擬的軟件。以此程序?yàn)榛A(chǔ),本文分別建立了描述支架膨脹綜合性能和柔順性能的數(shù)學(xué)模型,對目標(biāo)支架的幾何形狀及尺寸進(jìn)行了優(yōu)化,改善了目標(biāo)支架各項(xiàng)力學(xué)性能。以往在血管支架設(shè)計(jì)領(lǐng)域里采用的傳統(tǒng)模式是對有限數(shù)量的設(shè)計(jì)方案分別進(jìn)行數(shù)值模擬或?qū)嶒?yàn)分析,然后比較支架的力學(xué)性能結(jié)果并進(jìn)行人工選優(yōu)。本文的優(yōu)化工作則將最優(yōu)化理論拓展到血管支架的設(shè)計(jì)工作,有效地提高了血管支架優(yōu)化設(shè)計(jì)工作的效率。
[Abstract]:Cardiovascular disease is a major disease that threatens the health of the residents. According to statistics, the number of people who die of cardiovascular disease annually is about three million, accounting for about 45% of the total death toll. The cost of medical treatment for cardiovascular diseases is more than 130 billion yuan per year. Coronary stent implantation is an effective means for the treatment of coronary heart disease. The mechanical properties of coronary stents are one of the key factors related to the effect of stenting. Many medical workers and engineering scholars are trying to study the subject. In this paper, the finite element method is used to study the mechanical properties of coronary stent.
The main work of the paper is as follows:
The effects of the element types (high order solid element, low order solid element, shell element, beam element) and mesh density on the calculation efficiency and accuracy are studied for the bare stent structure of the finite element model. The mechanical properties involved in the whole life of the coronary stents are simulated. In this paper, the compression deformation in the operation, the expansion deformation in the operation and the compression deformation in the long period of operation in the coronary artery are found in this paper. It is found that the influence of the compression process on the expansibility is small, and the expansion degree has a great influence on the radial support force against the compression load in the working state. In addition, the expansion performance curve of the support is based on the expansion performance. The expansion curve is obtained after in-depth analysis of the line, and the intrinsic relationship between the expansion speed curve and the optimum expansion range of the bracket is found.
In this paper, the contact problem between the coronary stents and the balloon was simulated and the result of a more accurate deformation was obtained. On this basis, the method of using the strain energy to calculate the real contact pressure was proposed. In general, the contact pressure between the balloon and the bracket obtained by the contact analysis is compared with the uniform pressure in the actual situation. The error is often relatively large, which is due to the finer metal wire of the bracket, which can only be caused by the use of a coarser mesh element on the contact surface. According to the function principle, the only direct reason for the strain energy generated by the expansion of the drive bracket is that the contact pressure is the percentage of the full strain energy to the expansion load. The charge is corrected and the actual and uniform contact pressure between the stent and the balloon is obtained. The result is consistent with the expansion curve of the bare scaffold. This method can be used as a basis to verify the correctness of the contact analysis results.
In view of the longitudinal flexibility of the coronary stent, a cantilever beam bending model has been established to overcome the defects of the three point load method and the simple supported beam model. It can describe the overall bending performance of the support more accurately and more comprehensively. Based on this model, the instantaneous flexural rigidity of the target bracket in a large curvature range is studied in detail, and the results are studied in detail. It is shown that the instantaneous bending stiffness of the bracket is usually isotropic when the bending curvature is small, and when the curvature of the bracket is large, there is a very obvious anisotropy. In addition, the cantilever beam model also shows that the lateral deflection outside the Wan Quping surface and the torsion around the center axis of the support are also accompanied by the cantilever beam model. The two incidental deformation is caused by the bending deformation of the bracket, which changes the actual bending direction and curvature of the bracket to a certain extent. The two incidental deformation is also the evidence of the anisotropy of the instantaneous bending stiffness.
In the optimization design, a program for the finite element analysis of coronary artery stents is developed using the APDL language of ANSYS. The program has the characteristics of automatic operation, parametric modeling, process analysis, robustness calculation and optimization. The program can be used as a special application for the mechanical performance of vascular stent. On the basis of this program, the mathematical model describing the comprehensive and compliant performance of the stent expansion is established in this paper. The geometry and size of the target support are optimized and the mechanical properties of the target support are improved. The traditional model used in the field of vascular stent design is a limited number of designs in the past. The numerical simulation and experimental analysis are carried out respectively, then the mechanical performance results of the support are compared and the artificial optimization is compared. The optimization work of this paper extends the optimization theory to the design work of the vascular scaffold, which effectively improves the efficiency of the optimization design of the vascular stent.

【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2011
【分類號】：R312

【引證文獻(xiàn)】

相關(guān)期刊論文 前1條

1 徐江;楊杰;楊基;游天雪;黃楠;;基于有限元方法的血管支架設(shè)計(jì)和研制[J];四川大學(xué)學(xué)報(bào)(工程科學(xué)版);2012年S2期

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本文編號：1895823