Tissue Mechanics Laboratory, The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States.
Tissue Mechanics Laboratory, The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States.
J Mech Behav Biomed Mater. 2018 Jan;77:649-659. doi: 10.1016/j.jmbbm.2017.10.022. Epub 2017 Oct 20.
The patient-specific biomechanical analysis of the aorta requires in vivo mechanical properties of individual patients. Existing approaches for estimating in vivo material properties often demand high computational cost and mesh correspondence of the aortic wall between different cardiac phases. In this paper, we propose a novel multi-resolution direct search (MRDS) approach for estimation of the nonlinear, anisotropic constitutive parameters of the aortic wall. Based on the finite element (FE) updating scheme, the MRDS approach consists of the following three steps: (1) representing constitutive parameters with multiple resolutions using principal component analysis (PCA), (2) building links between the discretized PCA spaces at different resolutions, and (3) searching the PCA spaces in a 'coarse to fine' fashion following the links. The estimation of material parameters is achieved by minimizing a node-to-surface error function, which does not need mesh correspondence. The method was validated through a numerical experiment by using the in vivo data from a patient with ascending thoracic aortic aneurysm (ATAA), the results show that the number of FE iterations was significantly reduced compared to previous methods. The approach was also applied to the in vivo CT data from an aged healthy human patient, and using the estimated material parameters, the FE-computed geometry was well matched with the image-derived geometry. This novel MRDS approach may facilitate the personalized biomechanical analysis of aortic tissues, such as the rupture risk analysis of ATAA, which requires fast feedback to clinicians.
患者特定的主动脉生物力学分析需要个体患者的体内力学特性。现有的估计体内材料特性的方法通常需要主动脉壁在不同心动周期之间的高计算成本和网格对应。在本文中，我们提出了一种新颖的多分辨率直接搜索（MRDS）方法，用于估计主动脉壁的非线性各向异性本构参数。基于有限元（FE）更新方案，MRDS 方法包括以下三个步骤：（1）使用主成分分析（PCA）用多个分辨率表示本构参数，（2）在不同分辨率的离散 PCA 空间之间建立链接，以及（3）按照链接以“从粗到细”的方式搜索 PCA 空间。材料参数的估计是通过最小化节点到曲面误差函数来实现的，该函数不需要网格对应。该方法通过使用升主动脉瘤（ATAA）患者的体内数据进行数值实验进行了验证，结果表明与以前的方法相比，FE 迭代次数显著减少。该方法还应用于老年健康人体的体内 CT 数据，并且使用估计的材料参数，FE 计算的几何形状与图像衍生的几何形状很好地匹配。这种新颖的 MRDS 方法可以促进主动脉组织的个性化生物力学分析，例如 ATAA 的破裂风险分析，这需要快速反馈给临床医生。
