The relationship between geometry and the distribution of stress within the struts of bioresorbable scaffolds

冠状动脉支架是用于恢复病变冠状动脉狭窄管腔直径的管状支架结构。最近生物可吸收支架的发展在临床结果方面显示出一些希望。然而，很明显，这些塑料装置的机械性能需要改进，以充分利用它们的好处。迄今为止，许多研究都采用了“宏观”方法来设计冠状动脉支架研究，因此寻求优化设计变量，如“连接器数量”或“环间距”。据我们所知，到目前为止，还没有工作考虑到在卷曲和膨胀中沿着设备轮廓开发的塑性应变，以及这如何影响设备的行为。虽然很少有研究记录了构建的CAD模型的参数化的细节，但似乎没有任何研究使用与此早期开发的相同方法开发，使用傅立叶级数来描述设备的轮廓。该项目旨在对这些支架在卷曲和膨胀后的轮廓周围的应力和应变分布进行详细分析。这种详细的分析将有助于我们了解塑料应变是如何以及在哪里沿着支架的结构被利用的，从而有助于设计具有改进机械性能的支架。这些知识可以潜在地应用于其他生物医学支架。将创建设备的参数化模型，以便方便地更改支架的几何形状，并在保持灵活设计的同时尽量减少设计变量的数量。将对一系列支架几何形状进行结构FEA（有限元分析），然后通过代理建模进行设计优化，以获得优化设计。

Coronary stents are tubular scaffold structures used to recover the lumen diameter of diseased coronary arteries that have narrowed. The recent development of bioresorbable stents has shown some promise in terms of clinical outcome. However, it is clear that the mechanical properties of these plastic devices need to be improved for their benefits to be fully exploited. Many studies to date have taken a 'macro' approach to design studies of coronary stents and hence seek to optimise design variables such as the 'number of connectors' or 'ring spacing'. To our knowledge no work to date considers the plastic strain exploited along the profile of the device in crimping and expansion and how this effects behaviour of the device. Whilst few studies document the detail of the parameterisation of the CAD models constructed it does not appear that any have been developed using the same method that was developed early in this utilising a Fourier series to describe the profile of the device. This project seeks to undertake a detailed analysis of the distribution of stress and strain around the profile of these scaffolds post crimping and expansion. This detailed analysis will aid our understanding of how and where plastic strain is exploited along the structure of the stent and in turn help to design scaffolds with improved mechanical properties. This knowledge can then potentially be applied to other biomedical scaffolds. A parametric model of the device will be created to allow for convenient changes to the geometry of the stent and seek to minimise the number of design variables whilst aintaining a flexible design. Structural FEA (finite element analysis) will be conducted on a range of stent geometries and then design optimisation via surrogate modelling will be carried out to obtain an optimised design.