Biomaterials Research Unit, Faculty of Dentistry, University of Sydney, Sydney Dental Hospital, 2 Chalmers Street, Surry Hills, NSW 2010, Australia.
J Dent Res. 2011 Jan;90(1):18-30. doi: 10.1177/0022034510378429. Epub 2010 Sep 21.
Accurate assessment of mineral density (MD) provides information critical to the understanding of mineralization processes of calcified tissues, including bones and teeth. High-resolution three-dimensional assessment of the MD of teeth has been demonstrated by relatively inaccessible synchrotron radiation microcomputed tomography (SRµCT). While conventional desktop µCT (CµCT) technology is widely available, polychromatic source and cone-shaped beam geometry confound MD assessment. Recently, considerable attention has been given to optimizing quantitative data from CµCT systems with polychromatic x-ray sources. In this review, we focus on the approaches that minimize inaccuracies arising from beam hardening, in particular, beam filtration during the scan, beam-hardening correction during reconstruction, and mineral density calibration. Filtration along with lowest possible source voltage results in a narrow and near-single-peak spectrum, favoring high contrast and minimal beam-hardening artifacts. More effective beam monochromatization approaches are described. We also examine the significance of beam-hardening correction in determining the accuracy of mineral density estimation. In addition, standards for the calibration of reconstructed grey-scale attenuation values against MD, including K(2)PHO(4) liquid phantom, and polymer-hydroxyapatite (HA) and solid hydroxyapatite (HA) phantoms, are discussed.
准确评估矿物质密度（MD）可提供有关矿化过程的关键信息，包括骨骼和牙齿的矿化过程。高分辨率的牙齿 MD 三维评估已经通过相对难以接近的同步辐射微计算机断层扫描（SRµCT）来实现。虽然传统的台式微计算机断层扫描（CµCT）技术广泛可用，但多色源和锥形束几何形状会干扰 MD 评估。最近，人们越来越关注优化具有多色 X 射线源的 CµCT 系统的定量数据。在这篇综述中，我们重点介绍了最小化由于束硬化引起的不准确性的方法，特别是在扫描过程中的束滤波、重建过程中的束硬化校正和矿物质密度校准。滤波以及尽可能低的源电压会导致谱线变窄且接近单峰，有利于高对比度和最小化束硬化伪影。描述了更有效的束单色化方法。我们还研究了束硬化校正在确定矿物质密度估计准确性方面的重要性。此外，讨论了针对重建灰度衰减值与 MD 校准的标准，包括 K(2)PHO(4) 液体体模、聚合物-羟基磷灰石（HA）和固体羟基磷灰石（HA）体模。
