The effects of geometric and threshold definitions on cortical bone metrics assessed by in vivo high-resolution peripheral quantitative computed tomography
The effects of geometric and threshold definitions on cortical bone metrics assessed by in vivo high-resolution peripheral quantitative computed tomography
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DOI：
10.1007/s00223-007-9076-3
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发表时间：
2007-11-01
影响因子：
4.2
通讯作者：
Majumdar, Sharmila
中科院分区：
文献类型：
--
作者：
Davis, Kevin A.;Burghardt, Andrew J.;Majumdar, Sharmila
这项研究评估了体内计算皮质厚度(Ct.Th)的方法，这些方法与矿化中组织水平变化的敏感性和预测全骨机械性能的能力有关。使用高分辨率外周定量计算机断层扫描(HR-pQCT)获得的正常志愿者的桡骨和胫骨远端图像，使用三个阈值进行分割，包括制造商的默认阈值和等值矿物质密度的+/-5%。CT Th的测定有两种方法：直接三维(3D)法和环形法，其中皮质骨体积除以骨膜表面积。D-comp(mg HA/cm(3))是根据平均密度校准的皮质室的线性衰减值计算的。通过有限元分析评价环状和直接Ct.Th方法的预测能力。使用直接3D方法，阈值每改变+/-5%，桡骨和胫骨的Ct.Th的平均差值均为2%。用环形法测得的平均误差为5%。阈值的改变导致胫骨和桡骨的D-comp变化在0.50-1.56%之间。环状Ct.Th与全骨表观模数的相关性更强(R-2=0.64比R-2=0.41)。厚度计算方法和阈值的选择都直接影响到从HR-pQCT图像中提取的皮质参数。间接地，这些结果表明，组织水平矿化的适度变化可以影响皮质测量。此外，虽然直接3D CT Th方法对阈值效应不那么敏感，但这两种方法都是机械强度的中等预测因子，其中环形方法相关性更强。
This study evaluates in vivo methods for calculating cortical thickness (Ct.Th) with respect to sensitivity to tissue-level changes in mineralization and the ability to predict whole-bone mechanical properties. Distal radial and tibial images obtained from normal volunteers using high-resolution peripheral quantitative computed tomography (HR-pQCT) were segmented using three thresholds including the manufacturer default and +/- 5% in terms of equivalent mineral density. Ct.Th was determined in two ways: using a direct three-dimensional (3D) method and using an annular method, where cortical bone volume is divided by periosteal surface area. D-comp (mg HA/cm(3)) was calculated based on the mean density-calibrated linear attenuation values of the cortical compartment. Finite element analysis was performed to evaluate the predictive ability of the annular and direct Ct.Th methods. Using the direct 3D method, a +/- 5% change in threshold resulted in a 2% mean difference in Ct.Th for both the radius and tibia. An average difference of 5% was found using the annular method. The change in threshold produced changes in D-comp ranging 0.50-1.56% for both the tibia and radius. Annular Ct.Th correlated more strongly with whole-bone apparent modulus (R-2 = 0.64 vs. R-2 = 0.41). Both thickness calculation methods and threshold selection have a direct impact on cortical parameters derived from HR-pQCT images. Indirectly, these results suggest that moderate changes in tissue-level mineralization can affect cortical measures. Furthermore, while the direct 3D Ct.Th method is less sensitive to threshold effects, both methods are moderate predictors of mechanical strength, with the annular method being the stronger correlate.