De Beule M, Van Impe R, Verhegghe B, Segers P, Verdonck P
Laboratory for Research on Structural Models, Faculty of Engineering, Department of Structural Engineering, Ghent University, Technologiepark-Zwijnaarde 904, B-9052 Zwijnaarde, Belgium.
Technol Health Care. 2006;14(4-5):233-41.
In Western countries, cardiovascular disease is the most common cause of death, often related to atherosclerosis. This paper offers a brief introduction into some aspects of this disease and its treatment, where the use of stents is gaining increasing importance. Stents are supporting - mostly metal - tubular mesh structures which are opened in an obstructed artery in order to reopen it, and to offer radial strength to prevent elastic recoil of the dilated vessel. In addition to a variety of experimental tests to study the behavior of (new) stent designs, advanced numerical models (e.g. Finite Element Models) may offer interesting insights in the mechanical behavior of stents and will undoubtedly influence the design of future generation stents. A brief literature review on numerical studies dealing with the mechanical behavior of stents is presented. Subsequently, the finite element method is exploited to investigate and compare different designs of a "first generation" Palmaz Schatz stent in order to reduce the dogboning (i.e. ends of stent open first during expansion) to a minimum. Our computational models (Abaqus ) are described in terms of geometry, constitutive material models, numerical aspects and output quantities. Altering the original symmetric stent design to asymmetric designs decreased the dogboning from 27.24% to less than 10% for the vast majority of the studied asymmetric designs. For one particular configuration, the dogboning effect vanished completely. For this reason, taking asymmetry into account in the design of stents seems very promising, at least from the perspective of dogboning. However, as the dogboning only takes into account the radii (R) at the central and distal part of the stent, nothing can be concluded concerning the uniformity of the complete stent expansion. The mean value (Rm) and the root mean square (R(RMS)) of radii (differences) of the stent at the end of the loading phase (P = 0.7 N/mm2) are much better parameters to give a clear indication of the uniformity of the expanded stent's shape. Although the model is suitable to study basic aspects of stent deployment, further research is necessary, especially accounting for newer generation stent geometries and more realistic balloon-stent interaction.
在西方国家，心血管疾病是最常见的死亡原因，通常与动脉粥样硬化有关。本文简要介绍了这种疾病及其治疗的一些方面，其中支架的使用正变得越来越重要。支架是一种支撑结构——大多为金属管状网状结构，在阻塞的动脉中展开以重新打通血管，并提供径向强度以防止扩张后的血管发生弹性回缩。除了各种用于研究（新型）支架设计性能的实验测试外，先进的数值模型（如有限元模型）可以为支架的力学性能提供有趣的见解，并且无疑会影响下一代支架的设计。本文对涉及支架力学性能的数值研究进行了简要的文献综述。随后，利用有限元方法研究并比较了“第一代”帕尔马兹·沙茨支架的不同设计，以将狗骨化现象（即支架在扩张过程中两端先张开）降至最低。我们的计算模型（Abaqus）从几何形状、本构材料模型、数值方面和输出量等方面进行了描述。将原始的对称支架设计改为不对称设计后，对于绝大多数研究的不对称设计，狗骨化现象从27.24%降至不到10%。对于一种特定的构型，狗骨化效应完全消失。因此，至少从狗骨化的角度来看，在支架设计中考虑不对称性似乎非常有前景。然而，由于狗骨化仅考虑了支架中心和远端部分的半径（R），所以无法得出关于整个支架扩张均匀性的结论。在加载阶段结束时（P = 0.7 N/mm²）支架半径（差异）的平均值（Rm）和均方根（R(RMS)）是能更清楚地表明扩张后支架形状均匀性的更好参数。尽管该模型适用于研究支架展开的基本方面，但仍需要进一步研究，特别是考虑新一代支架的几何形状以及更现实的球囊 - 支架相互作用。
