High-resolution magnetic resonance imaging: Three-dimensional trabecular bone architecture and biomechanical properties
High-resolution magnetic resonance imaging: Three-dimensional trabecular bone architecture and biomechanical properties
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DOI：
10.1016/s8756-3282(98)00030-1
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发表时间：
1998-05-01
期刊：
影响因子：
4.1
通讯作者：
Genant, HK
中科院分区：
文献类型：
--
作者：
Majumdar, S;Kothari, M;Genant, HK
本研究的目的是利用高分辨率磁共振 (MR) 成像结合图像分析来研究人体椎骨、股骨和跟骨标本的三维 (3D) 小梁结构、各向异性和连接性。目标是确定是否：(a) MR 衍生测量描述了小梁结构和方向上已知的骨骼部位特异性差异； (b) 3D 结构参数与骨矿物质密度 (BMD) 相结合，使用织物张量公式改进了弹性模量的预测； (c) MR 衍生的 3D 结构参数与 BMD 相结合，使用多元回归模型改进了强度预测，以及这些结果是否与使用更高分辨率的小梁结构描述获得的结果相对应。总共获得了 94 个仅由骨小梁组成的标本（12 x 12 x 12 mm 立方体），其中 7 个来自跟骨，15 个来自股骨远端，47 个来自股骨近端，25 个来自椎体。使用 1.5 Tesla MR 扫描仪以 117 x 117 x 300 μm 的空间分辨率获得 MR 图像。此外，使用定量计算机断层扫描 (QCT) 确定 BMD，并对标本进行无损测试，并沿着对应于解剖上下（轴向）、内侧-外侧（矢状）和前后（冠状）方向的三个正交轴测量弹性模量（YM），然后在上下（轴向）方向对标本子集（n = 67）进行破坏性测试，以测量弹性模量（YM）。极限抗压强度。 MR 图像被分割为骨相和骨髓相，然后进行 3D 分析。使用单值分解和小梁的主要方向将椭球拟合到平均截距长度，并用于计算小梁结构的各向异性。使用先前开发的模型得出体视学测量值，并得出平均小梁宽度、间距和数量等测量值。由于 NBR 图像的空间分辨率与小梁骨尺寸相当，因此这些测量值可能会受到部分体积效应的影响，因此被视为表观测量值，例如 BV/TV、Tb.Sp、Tb.N 和 Tb.Th，而不是从组织形态计量学得出的绝对测量值。此外，在样本子集中，确定每单位体积的欧拉数来表征小梁网络的连通性。不同骨骼部位的骨密度、小梁结构测量、弹性模量和强度存在显着差异。大多数标本的主要方向轴是解剖学的上下（轴向）方向。使用织物张量公式，除了 BMD 之外，还改进了 YM (SI) 的预测，同时包含一些结构参数，显着改进了强度的预测。将 MR 衍生的 3D 测量值与从 20 μ m 光学图像（n = 18；9 个椎骨，9 个股骨标本）获得的测量值进行比较时，发现表观 Tb.Sp 和 Tb.N 具有良好的相关性，表观 BV/TV 具有中等相关性，而表观 Tb.Th 则具有较差的相关性。使用这些更高分辨率的图像，用于预测弹性模量的织物张量公式还显示出轴向（SI）方向上测量的模量和计算的模量之间的相关性得到改善。总之，高分辨率 MR 图像可用于评估骨小梁的 3D 结构，并且包含一些 3D 结构测量可提供对生物力学特性的改进评估。显然需要进一步的研究来确定结构在预测整体骨质量中的作用，以及小梁结构测量在临床实践中的作用。目前，MR 技术可能无法替代组织形态计量学；然而，它们可以提供一个理想的平台，用于纵向评估体内多个骨骼部位的小梁结构，并有助于了解骨质疏松症和衰老变化的病因，研究骨质疏松症的进展和治疗效果。 (C) 1998 年，Elsevier Science Inc. 保留所有权利。
The purpose of this study was to use high-resolution magnetic resonance (MR) imaging combined with image analysis to investigate the three-dimensional (3D) trabecular structure, anisotropy, and connectivity of human vertebral, femoral, and calcaneal specimens. The goal was to determine whether: (a) MR-derived measures depict known skeletal-site-specific differences in architecture and orientation of trabeculae; (b) 3D architectural parameters combined with bone mineral density (BMD) improve the prediction of the elastic modulus using a fabric tensor formulation; (c) MR-derived 3D architectural parameters combined with BMD improve the prediction of strength using a multiple regression model, and whether these results corresponded to the results obtained using higher resolution depictions of trabecular architecture. A total of 94 specimens (12 x 12 x 12 mm cubes) consisting of trabecular bone only were obtained, of which there were 7 from the calcaneus, 15 from distal femur, 47 from the proximal femur, and 25 from the vertebral bodies. MR images were obtained using a 1.5 Tesla MR scanner at a spatial resolution of 117 x 117 x 300 mu m. Additionally, BMD was determined using quantitative computed tomography (QCT), and the specimens were nondestructively tested and the elastic modulus (YM) was measured along three orthogonal axes corresponding to the anatomic superior-inferior (axial), medial-lateral (sagittal), and anterior-posterior (coronal) directions, the subset of the specimens (n = 67) was then destructively tested in the superior-inferior (axial) direction to measure the ultimate compressive strength. The MR images were segmented into bone and marrow phases and then analyzed in 3D. Ellipsoids were fitted to the mean intercept lengths, using single value decomposition and the primary orientation of the trabeculae and used to calculate the anisotropy of trabecular architecture. Stereological measures were derived using a previously developed model and measures such as mean trabecular width, spacing, and number were derived. Because the spatial resolution of NBR images is comparable to trabecular bone dimensions, these measures may be subject to partial volume effects and were thus treated as apparent measures, such as BV/TV, Tb.Sp, Tb.N, and Tb.Th rather than absolute measures, as would be derived from histomorphometry.In addition, in a subset of specimens, the Euler number per unit volume was determined to characterize the connectivity of the trabecular network. There were significant differences in the BMD, trabecular architectural measures, elastic modulus, and strength at the different skeletal sites. The primary orientation axes for most of the specimens was the anatomic superior-inferior (axial) direction. Using the fabric tensor formulation, in addition to BMD, improved the prediction of YM (SI), while including some of the architectural parameters significantly improved the prediction of strength. In comparing MR-derived 3D measures with those obtained from 20 mu m optical images (n = 18; 9 vertebrae, 9 femur specimens), good correlations were found for the apparent Tb.Sp and Tb.N, moderate correlation was seen for the apparent BV/TV, and poor correlation was found for the apparent Tb.Th. Using these higher resolution images, the fabric tensor formulation for predicting the elastic modulus also showed improved correlation between the measured and calculated modulus in the axial (SI) direction. In summary, high-resolution MR images may be used to assess 3D architecture of trabecular bone, and the inclusion of some of the 3D architectural measures provides an improved assessment of biomechanical properties. Further studies are clearly warranted to establish the role of architecture in predicting overall bone quality, and the role of trabecular architecture measures in clinical practice. Currently, MR techniques may not be used instead of histomorphometry; however, they may provide an ideal platform for assessing trabecular architecture in vivo, at multiple skeletal sites longitudinally, and assist in understanding the etiology of osteoporotic and aging changes, for studying osteoporosis progression and therapeutic efficacy. (C) 1998 by Elsevier Science Inc. All rights reserved.