Duryea J, Dobbins J T, Lynch J A
Osteoporosis and Arthritis Research Group, Department of Radiology, University of California, San Francisco, San Francisco, California 94143, USA.
Med Phys. 2003 Mar;30(3):325-33. doi: 10.1118/1.1543573.
The two principal forms of hand arthritis, rheumatoid arthritis (RA) and osteoarthritis (OA) have large clinical and economic costs. Radiography has been shown to be a useful tool to assess the condition of the disease. A hand radiograph, however, is a two-dimensional projection of a three-dimensional object. In this report we present the results of a study that applied digital tomosynthesis to hand radiography in order to extract three-dimensional outcome measures that should be more sensitive to arthritis progression. The study was performed using simulated projection radiographs created using micro computed tomography (microCT) and a set of five dry-bone hand skeletons. These simulated projection images were then reconstructed into tomographic slices using the matrix inversion tomosynthesis (MITS) algorithm. The accuracy of the tomosynthesis reconstruction was evaluated by comparing the reconstructed images to a gold standard created using the microCT data. A parameter from image registration science, normalized mutual information, provided a quantifiable figure of merit. This study examined the effects of source displacement, number of reconstructed planes, number of acquisitions, noise added to the gray scale images, and errors in the location of a fiducial marker. We also optimized the reconstruction as a function of two variables k and alpha, that controlled the mixing of MITS with conventional shift-and-add tomosynthesis. A study using hand delineated joint margins demonstrated that MITS images provided a better measurement of average joint space width. We found good agreement between the MITS slices and the true planes. Both joint margins and trabecular structure were visible and the reconstructed slices showed additional structures not visible with the standard projection image. Using hand-delineated joint margins we compared the average joint space width of the gold standard slices to the MITS and projection images. A root-mean square deviation (RMSD), calculated for this comparison, gave RMSDproj = 0.18 mm and RMSDMITS = 0.14 mm for the projection and MITS images, respectively. We have demonstrated the potential of digital tomosynthesis for imaging of the hand to assess arthritic changes. We have also developed a methodology that can be used to optimize the technique and have studied the issues that will control the feasibility of clinical implementation.
手部关节炎的两种主要形式，类风湿性关节炎（RA）和骨关节炎（OA），会带来巨大的临床和经济成本。放射成像已被证明是评估疾病状况的有用工具。然而，手部X光片是三维物体的二维投影。在本报告中，我们展示了一项研究的结果，该研究将数字断层合成技术应用于手部放射成像，以提取对关节炎进展更敏感的三维结果指标。该研究使用了通过微型计算机断层扫描（microCT）创建的模拟投影X光片和一组五个手部干骨骨骼。然后使用矩阵反演断层合成（MITS）算法将这些模拟投影图像重建为断层切片。通过将重建图像与使用microCT数据创建的金标准进行比较，评估了断层合成重建的准确性。图像配准科学中的一个参数，归一化互信息，提供了一个可量化的品质因数。本研究考察了源位移、重建平面数量、采集数量、添加到灰度图像的噪声以及基准标记位置误差的影响。我们还根据两个变量k和alpha对重建进行了优化，这两个变量控制了MITS与传统移位相加断层合成的混合。一项使用手部勾勒关节边缘的研究表明，MITS图像能更好地测量平均关节间隙宽度。我们发现MITS切片与真实平面之间有很好的一致性。关节边缘和小梁结构都清晰可见，并且重建切片显示出标准投影图像中不可见的额外结构。使用手部勾勒的关节边缘，我们将金标准切片的平均关节间隙宽度与MITS图像和投影图像进行了比较。为此比较计算的均方根偏差（RMSD），投影图像和MITS图像的RMSDproj分别为0.18毫米和RMSDMITS = 0.14毫米。我们已经证明了数字断层合成技术在手部成像以评估关节炎变化方面的潜力。我们还开发了一种可用于优化该技术的方法，并研究了将控制临床实施可行性的问题。
