Estimation of 3D shape, internal density and mechanics of proximal femur by combining bone mineral density images with shape and density templates
Estimation of 3D shape, internal density and mechanics of proximal femur by combining bone mineral density images with shape and density templates
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DOI：
10.1007/s10237-011-0352-9
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发表时间：
2012-07-01
影响因子：
3.5
通讯作者：
Isaksson, Hanna
中科院分区：
文献类型：
--
作者：
Vaananen, Sami P.;Jurvelin, Jukka S.;Isaksson, Hanna
单用双能x线骨密度仪（DXA）测量骨密度（BMD）仅是骨折风险的中等预测指标。基于DXA图像的骨力学有限元分析（FEA）可以提高骨折风险的预测。我们开发了一种方法来估计股骨近端三维形状和密度分布，使用二维BMD图像和股骨形状模板。对18具人体尸体的近端股骨进行计算机断层成像，并将其分为两组（N = 9 + 9）。利用三维广义Procrustes分析和薄板样条法从第一组样品中创建模板。随后，利用模板和二维BMD图像估计第二组股骨的形状和内部密度分布。最后，基于原始骨模型和预估骨模型进行有限元分析，评估几何和密度分布误差对机械强度的影响。估计本身引起的体积误差很低（< 1.4%）。在第二组骨的估计中，估计的骨表面与原始骨表面的平均距离差为0.80±0.19 mm，表明对股骨形状的估计是可行的。逐体素BMD的平均绝对误差为120 +/- 8 mg cm（-3）。在有限元分析中，股骨近端刚度在原始骨和估计骨之间相差-7 +/- 16%。与以往的研究方法相比，本方法改进了对股骨近端几何形状、骨密度分布和力学特性的预测。潜在地，提出的方法可以最终提高骨折风险的确定。
Measurement of bone mineral density (BMD) by dual-energy X-ray absorptiometry (DXA) alone is only a moderate predictor of fracture risk. Finite element analysis (FEA) of bone mechanics, based on DXA images, may improve the prediction of fracture risk. We developed a method to estimate the 3D shape and density distribution of the proximal femur, using a 2D BMD image and a femur shape template. Proximal femurs of eighteen human cadavers were imaged using computed tomography and divided into two sets (N = 9 + 9). The template was created from the samples in first set by using 3D generalized Procrustes analysis and thin-plate splines. Subsequently, the template and 2D BMD image were utilized to estimate the shape and internal density distribution of the femurs in the second set. Finally, FEA was conducted based on the original and the estimated bone models to evaluate the effect of geometrical and density distributional errors on the mechanical strength. The volumetric errors induced by the estimation itself were low (< 1.4%). In the estimation of bones in the second set, the mean distance difference between the estimated and the original bone surfaces was 0.80 +/- 0.19 mm, suggesting feasible estimation of the femoral shape. The mean absolute error in voxel-by-voxel BMD was 120 +/- 8 mg cm(-3). In FEA, the stiffness of the proximal femur differed by -7 +/- 16% between the original and estimated bones. The present method, in comparison with methods used in previous studies, improved the prediction of the geometry, the BMD distribution and the mechanical characteristics of the proximal femur. Potentially, the proposed method could ultimately improve the determination of bone fracture risk.