Guha Indranil, Zhang Xialiou, Rajapakse Chamith S, Letuchy Elena M, Chang Gregory, Janz Kathleen F, Torner James C, Levy Steven M, Saha Punam K
Department of Electrical and Computer Engineering University of Iowa Iowa City IA USA.
Departments of Radiology and Orthopedic Surgery University of Pennsylvania Philadelphia PA USA.
JBMR Plus. 2022 May 5;6(6):e10627. doi: 10.1002/jbm4.10627. eCollection 2022 Jun.
Osteoporosis causes bone fragility and elevates fracture risk. Applications of finite element (FE) analysis (FEA) for assessment of trabecular bone (Tb) microstructural strength at whole-body computed tomography (CT) imaging are limited due to challenges with Tb microstructural segmentation. We present a nonlinear FEA method for distal tibia CT scans evading binary segmentation of Tb microstructure, while accounting for bone microstructural distribution. First, the tibial axis in a CT scan was aligned with the FE loading axis. FE cubic mesh elements were modeled using image voxels, and CT intensity values were calibrated to ash density defining mechanical properties at individual elements. For FEA of an upright volume of interest (VOI), the bottom surface was fixed, and a constant displacement was applied at each vertex on the top surface simulating different loading conditions. The method was implemented and optimized using the ANSYS software. CT-derived computational modulus values were repeat scan reproducible (intraclass correlation coefficient [ICC] ≥ 0.97) and highly correlated ( ≥ 0.86) with the micro-CT (μCT)-derived values. FEA-derived von Mises stresses over the segmented Tb microregion were significantly higher ( < 1 × 10) than that over the marrow space. In vivo results showed that both shear and compressive modulus for males were higher ( < 0.01) than for females. Effect sizes for different modulus measures between males and females were moderate-to-high (≥0.55) and reduced to small-to-negligible (<0.40) when adjusted for pure lean mass. Among body size and composition attributes, pure lean mass and height showed highest ( ∈ [0.45 0.56]) and lowest ( ∈ [0.25 0.39]) linear correlation, respectively, with FE-derived modulus measures. In summary, CT-based nonlinear FEA provides an effective surrogate measure of Tb microstructural stiffness, and the relaxation of binary segmentation will extend the scope for FEA in human studies using in vivo imaging at relatively low-resolution. © 2022 The Authors. published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.
骨质疏松症会导致骨骼脆弱并增加骨折风险。由于小梁骨（Tb）微观结构分割存在挑战，有限元（FE）分析（FEA）在全身计算机断层扫描（CT）成像中用于评估Tb微观结构强度的应用受到限制。我们提出了一种用于胫骨远端CT扫描的非线性FEA方法，该方法无需对Tb微观结构进行二值分割，同时考虑了骨微观结构分布。首先，将CT扫描中的胫骨轴与FE加载轴对齐。使用图像体素对FE立方网格单元进行建模，并将CT强度值校准为灰密度，以定义各个单元的力学性能。对于感兴趣的直立体积（VOI）进行FEA时，底面固定，并在顶面的每个顶点施加恒定位移以模拟不同的加载条件。该方法使用ANSYS软件进行实现和优化。基于CT得出的计算模量值在重复扫描时具有可重复性（组内相关系数[ICC]≥0.97），并且与基于微CT（μCT）得出的值高度相关（≥0.86）。在分割的Tb微区域上，FEA得出的冯·米塞斯应力明显高于骨髓空间上的应力（<1×10）。体内结果表明，男性的剪切模量和压缩模量均高于女性（<0.01）。男性和女性之间不同模量测量的效应大小为中到高（≥0.55），在调整纯瘦体重后降至小到可忽略不计（<0.40）。在身体大小和组成属性中，纯瘦体重和身高与基于FE得出的模量测量的线性相关性分别最高（∈[0.45 0.56]）和最低（∈[0.25 0.39]）。总之，基于CT的非线性FEA提供了一种有效的Tb微观结构刚度替代测量方法，并且放宽二值分割将扩大FEA在使用相对低分辨率体内成像的人体研究中的应用范围。©2022作者。由Wiley Periodicals LLC代表美国骨与矿物质研究学会出版。
