Finite element is an effective tool to simulate stent expansion inside stenotic arteries, which provides an insightful understanding of the biomechanical behaviour of the whole stent-artery system during the procedure. The choice of balloon type, system constraint and artery constitutive model plays an important role in finite element simulation of stent deployment. Commercial finite element package ABAQUS was used to model the expansion of Xience stent inside a diseased artery with 40% stenosis. The arterial wall, consisting of intima, media and adventitia layers, and the stenotic plaque were described by different hyperelastic models. Both folded and rubber balloons were considered and inflated with a linearly increasing pressure of 1.4 MPa. Simulations were also carried out by considering free, partially and fully constrained arteries. Folded balloon produces sustained stent expansion under a lower pressure when compared to rubber balloon, leading to increased stress level and enhanced final expansion for the system. Fully constrained artery reduces the stent expansion when compared to free and partially constrained arteries, due to the increased recoiling effect. Stress in the artery-plaque system has higher magnitude for stent expansion in a free artery due to more severe stretch. Calcified plaque limits stent expansion considerably when compared to hypocellular plaque. The negligence of the second stretch invariant in the strain energy potential leads to the disappearance of saturation behaviour during stent expansion. The use of anisotropic artery model reduces the system expansion at peak pressure when compared to the isotropic model, but with an increased final diameter due to reduced recoiling effect. The stress distribution in the artery-plaque system is also different for different combinations of artery and plaque constitutive models. Folded balloon should be used in the simulation of stent deployment, with the artery partially constrained using spring elements with a proper stiffness constant. The blood vessel should be modelled as a three-layer structure using a hyperelastic potential that considers both the first and second stretch invariants as well as the anisotropy. The composition of the plaque also has to be considered due to its major effect on stent deployment.

中文翻译：

---

用于支架展开的有限元模拟的球囊类型，系统约束和动脉本构模型的研究

有限元是模拟狭窄动脉内支架扩张的有效工具，可在手术过程中对整个支架-动脉系统的生物力学行为提供深刻的了解。气囊类型，系统约束和动脉本构模型的选择在支架展开的有限元模拟中起着重要作用。商业有限元软件包ABAQUS用于模拟Xience支架在狭窄程度为40％的患病动脉内的膨胀。由不同的超弹性模型描述了由内膜，中膜和外膜层组成的动脉壁和狭窄斑块。考虑了折叠气球和橡胶气球，并以线性增加的1.4 MPa的压力对其进行了充气。还通过考虑自由，部分和完全约束的动脉来进行模拟。与橡胶球囊相比，折叠球囊在较低压力下可产生持续的支架扩张，从而导致应力水平增加和系统最终扩张增强。与自由和部分受约束的动脉相比，完全受约束的动脉减少了支架的扩张，这是由于增加了回缩效果。由于更严重的拉伸，动脉斑块系统中的应力对于游离动脉中的支架扩张具有更高的强度。与低细胞斑块相比，钙化斑块极大地限制了支架的扩张。应变能势中第二个拉伸不变量的疏忽导致支架扩张过程中饱和行为的消失。与各向同性模型相比，各向异性动脉模型的使用减少了峰值压力下的系统扩展，但由于降低了回弹效果，最终直径增加了。对于动脉和斑块本构模型的不同组合，动脉斑块系统中的应力分布也不同。在支架的模拟中应使用折叠式气囊，使用具有适当刚度常数的弹簧元件将动脉部分约束。应使用考虑了第一和第二拉伸不变性以及各向异性的超弹性势将血管建模为三层结构。由于其对支架展开的主要影响，还必须考虑斑块的组成。在支架的模拟中应使用折叠式气囊，使用具有适当刚度常数的弹簧元件将动脉部分约束。应使用考虑了第一和第二拉伸不变性以及各向异性的超弹性势将血管建模为三层结构。由于其对支架展开的主要影响，还必须考虑斑块的组成。在支架的模拟中应使用折叠式气囊，并使用具有适当刚度常数的弹簧元件将动脉部分约束。应使用考虑了第一和第二拉伸不变性以及各向异性的超弹性势将血管建模为三层结构。由于其对支架展开的主要影响，还必须考虑斑块的组成。