Kothari M, Keaveny T M, Lin J C, Newitt D C, Genant H K, Majumdar S
Magnetic Resonance Science Center & Osteoporosis and Arthritis Research Group, Department of Radiology, University of California, San Francisco 94143, USA.
Bone. 1998 May;22(5):437-43. doi: 10.1016/s8756-3282(98)00031-3.
Although the efficacy of various measures for the assessment of trabecular bone architecture has been widely studied, the impact of spatial resolution on the estimation of these measures has remained relatively unexplored. In this study, ten cubes each of human trabecular bone from the femur and vertebral bodies were obtained from nine cadavers (four males and five females), aged 23-67 years (mean 42.3 years). These specimens were serially milled and imaged at a resolution of 40 microm to produce three-dimensional digitizations from which traditional morphometric and structural anisotropy measures could be computed based on a three-dimensional approach. The cubes were then artificially degraded to an in-plane resolution of 100 microm and an out-of-plane (slice) resolution of 100-1000 microm. These resolutions mimicked in vivo resolutions as seen using magnetic resonance (MR) imaging. All images, original and degraded, were individually segmented using a thresholding algorithm, and both the traditional morphometric and structural anisotropy measures were recomputed. The choice of slice direction was varied along the superior-inferior (axial), anterior-posterior (coronal), and medial-lateral (sagittal) directions to minimize the impact of the lower slice resolution on the architectural measures. It was found that traditional morphometric measures such as trabecular spacing and trabecular number showed weak resolution dependency; measures such as trabecular thickness, however, showed strong resolution dependency and required very high resolutions for precise measurement. In the case of the femur specimens, both structural anisotropy as well as the preferred orientation showed a strong resolution dependency. The resolution dependency of these parameters could be minimized for the femur and the vertebral body specimens if the slice direction was taken along the superior-inferior direction.
尽管评估小梁骨结构的各种方法的有效性已得到广泛研究，但空间分辨率对这些方法估计的影响仍相对未被探索。在本研究中，从9具年龄在23 - 67岁（平均42.3岁）的尸体（4名男性和5名女性）中获取了来自股骨和椎体的各10个小梁骨立方体。这些标本被连续研磨并以40微米的分辨率成像，以生成三维数字化图像，从中可以基于三维方法计算传统的形态计量学和结构各向异性测量值。然后将这些立方体人为降解至平面分辨率为100微米，平面外（切片）分辨率为100 - 1000微米。这些分辨率模拟了使用磁共振（MR）成像所见的体内分辨率。使用阈值算法对所有原始图像和降解后的图像进行单独分割，并重新计算传统的形态计量学和结构各向异性测量值。切片方向的选择沿着上下（轴向）、前后（冠状）和内外（矢状）方向变化，以尽量减少较低切片分辨率对结构测量的影响。结果发现，传统的形态计量学测量值，如小梁间距和小梁数量，显示出较弱的分辨率依赖性；然而，小梁厚度等测量值显示出较强的分辨率依赖性，并且需要非常高分辨率才能进行精确测量。对于股骨标本，结构各向异性以及优选取向均显示出较强的分辨率依赖性。如果切片方向沿着上下方向，则股骨和椎体标本这些参数的分辨率依赖性可以最小化。
