Tkachenko Evgeniy V, Slyfield Craig R, Tomlinson Ryan E, Daggett Justin R, Wilson David L, Hernandez Christopher John
Musculoskeletal Mechanics and Materials Laboratory, Department of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland, OH 44106, USA.
Bone. 2009 Sep;45(3):487-92. doi: 10.1016/j.bone.2009.05.019. Epub 2009 May 28.
Cavities formed by osteoclasts on the surface of cancellous bone during bone remodeling (resorption cavities) are believed to act as stress risers and impair cancellous bone strength and stiffness. Although resorption cavities are readily detected as eroded surfaces in histology sections, identification of resorption cavities in three-dimensional images of cancellous bone has been rare. Here we use sub-micrometer resolution images of rat lumbar vertebral cancellous bone obtained through serial milling (n=5) to determine how measures of the number and surface area of resorption cavities are influenced by image resolution. Three-dimensional images of a 1 mm cube of cancellous bone were collected at 0.7x0.7x5.0 microm/voxel using fluorescence based serial milling and uniformly coarsened to four other resolutions ranging from 1.4x1.4x5.0 to 11.2x11.2x10 microm/voxel. Cavities were identified in the three-dimensional image as an indentation on the cancellous bone surface and were confirmed as eroded surfaces by viewing two-dimensional cross-sections (mimicking histology techniques). The number of cavities observed in the 0.7x0.7x5.0 microm/voxel images (22.0+/-1.43, mean+/-SD) was not significantly different from that in the 1.4x1.4x5.0 microm/voxel images (19.2+/-2.59) and an average of 79% of the cavities observed at both of these resolutions were coincident. However, at lower resolutions, cavity detection was confounded by low sensitivity (<20%) and high false positive rates (>40%). Our results demonstrate that when image voxel size exceeds 1.4x1.4x5.0 microm/voxel identification of resorption cavities by bone surface morphology is highly inaccurate. Experimental and computational studies of resorption cavities in three-dimensional images of cancellous bone may therefore require images to be collected at resolutions of 1.4 microm/pixel in-plane or better to ensure consistent identification of resorption cavities.
在骨重塑过程中破骨细胞在松质骨表面形成的腔隙（吸收腔）被认为是应力集中源，会损害松质骨的强度和刚度。尽管吸收腔在组织学切片中很容易被检测为侵蚀表面，但在松质骨的三维图像中识别吸收腔却很少见。在这里，我们使用通过连续铣削获得的大鼠腰椎松质骨的亚微米分辨率图像（n = 5）来确定吸收腔数量和表面积的测量值如何受到图像分辨率的影响。使用基于荧光的连续铣削以0.7x0.7x5.0微米/体素的分辨率收集1立方毫米松质骨的三维图像，并均匀粗化到从1.4x1.4x5.0到11.2x11.2x10微米/体素的其他四种分辨率。在三维图像中，腔隙被识别为松质骨表面的凹陷，并通过查看二维横截面（模拟组织学技术）确认为侵蚀表面。在0.7x0.7x5.0微米/体素图像中观察到的腔隙数量（22.0±1.43，平均值±标准差）与在1.4x1.4x5.0微米/体素图像中观察到的数量（19.2±2.59）没有显著差异，并且在这两种分辨率下观察到的腔隙平均有79%是一致的。然而，在较低分辨率下，腔隙检测因低灵敏度（<20%）和高假阳性率（>40%）而受到混淆。我们的结果表明，当图像体素大小超过1.4x1.4x5.0微米/体素时，通过骨表面形态识别吸收腔非常不准确。因此，在松质骨三维图像中对吸收腔进行实验和计算研究可能需要以平面分辨率1.4微米/像素或更高来收集图像，以确保对吸收腔的一致识别。
