Improved accuracy of cortical bone mineralization measured by polychromatic microcomputed tomography using a novel high mineral density composite calibration phantom
Improved accuracy of cortical bone mineralization measured by polychromatic microcomputed tomography using a novel high mineral density composite calibration phantom
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DOI：
10.1118/1.3480507
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发表时间：
2010-09-01
期刊：
影响因子：
3.8
通讯作者：
Roeder, Ryan K.
中科院分区：
文献类型：
--
作者：
Deuerling, Justin M.;Rudy, David J.;Roeder, Ryan K.
目的：微计算机断层扫描（micro-CT）越来越多地用作灰化的非破坏性替代方法，用于测量骨矿物质含量。骨密度计用于将测量的X射线衰减校准到离散的矿物质密度水平，通常包括高达1000 mg HA/cm（3）的水平，其包括在骨小梁中观察到的骨矿物质密度（BMD）水平。然而，在皮质骨中观察到的BMD水平以及皮质骨和松质骨中的组织矿物质密度（TMD）水平通常超过1000 mg HA/cm（3），需要外推校准回归，这可能导致误差。因此，本研究的目的是研究（1）X射线衰减与衰减较小的聚合物基质中羟基磷灰石（HA）密度的扩展范围之间的关系，以及（2）校准对人体皮质骨标本中矿化的后续测量准确性的影响。方法：制备了一种新型HA-聚合物复合体模，（聚乙烯）和扩大范围的HA密度（0-1860 mg HA/cm（3）），包括皮质骨中BMD或皮质骨和小梁骨中TMD的特征水平。使用新的HA-聚合物校准体模测量的皮质骨样本的BMD和TMD与使用常规HA-聚合物体模的测量结果进行了比较，所述常规HA-聚合物体模包含0-800 mg HA/cm（3）以及相同样本上的相应灰分密度测量结果。HA-聚合物复合体模在X射线衰减和HA密度之间表现出非线性关系，而不是通常采用的先验线性关系，并且当将测量的X射线衰减校准到高水平的矿物密度时，避免了外推的需要。使用传统体模测量的皮质骨样本的BMD和TMD平均分别显著低于测量的灰分密度19%（p < 0.001，ANCOVA）和33%（p < 0.05，Tukey's HSD）。使用HA-聚合物体模测量的皮质骨标本的BMD和TMD与HA密度的扩展范围相比显著低于测量的灰密度8%（p < 0.001，ANCOVA）和10%（p < 0.05，Tukey's HSD）。新的HA聚合物校准体模具有更少的衰减聚合物和更大范围的HA密度，导致更准确的微与传统体模相比，人体皮质骨标本中的CT等效BMD和TMD，通过对相同标本的灰分密度测量进行验证。(C)2010年美国医学物理学家协会。[DOI 10.1118/1.3480507]
Purpose: Microcomputed tomography (micro-CT) is increasingly used as a nondestructive alternative to ashing for measuring bone mineral content. Phantoms are utilized to calibrate the measured x-ray attenuation to discrete levels of mineral density, typically including levels up to 1000 mg HA/cm(3), which encompasses levels of bone mineral density (BMD) observed in trabecular bone. However, levels of BMD observed in cortical bone and levels of tissue mineral density (TMD) in both cortical and trabecular bone typically exceed 1000 mg HA/cm(3), requiring extrapolation of the calibration regression, which may result in error. Therefore, the objectives of this study were to investigate (1) the relationship between x-ray attenuation and an expanded range of hydroxyapatite (HA) density in a less attenuating polymer matrix and (2) the effects of the calibration on the accuracy of subsequent measurements of mineralization in human cortical bone specimens.Methods: A novel HA-polymer composite phantom was prepared comprising a less attenuating polymer phase (polyethylene) and an expanded range of HA density (0-1860 mg HA/cm(3)) inclusive of characteristic levels of BMD in cortical bone or TMD in cortical and trabecular bone. The BMD and TMD of cortical bone specimens measured using the new HA-polymer calibration phantom were compared to measurements using a conventional HA-polymer phantom comprising 0-800 mg HA/cm(3) and the corresponding ash density measurements on the same specimens.Results: The HA-polymer composite phantom exhibited a nonlinear relationship between x-ray attenuation and HA density, rather than the linear relationship typically employed a priori, and obviated the need for extrapolation, when calibrating the measured x-ray attenuation to high levels of mineral density. The BMD and TMD of cortical bone specimens measured using the conventional phantom was significantly lower than the measured ash density by 19% (p < 0.001, ANCOVA) and 33% (p < 0.05, Tukey's HSD), on average, respectively. The BMD and TMD of cortical bone specimens measured using the HA-polymer phantom with an expanded range of HA density was significantly lower than the measured ash density by 8% (p < 0.001, ANCOVA) and 10% (p < 0.05, Tukey's HSD), on average, respectively.Conclusions: The new HA-polymer calibration phantom with a less attenuating polymer and an expanded range of HA density resulted in a more accurate measurement of micro-CT equivalent BMD and TMD in human cortical bone specimens compared to a conventional phantom, as verified by ash density measurements on the same specimens. (C) 2010 American Association of Physicists in Medicine. [DOI: 10.1118/1.3480507]