Talbot phase-contrast x-ray imaging for the small joints of the hand.
Talbot phase-contrast x-ray imaging for the small joints of the hand.
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DOI：
10.1088/0031-9155/56/17/015
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发表时间：
2011-09-07
影响因子：
3.5
通讯作者：
Bingham CO
中科院分区：
文献类型：
--
作者：
Stutman D;Beck TJ;Carrino JA;Bingham CO
手部小关节软组织的高分辨率放射学方法将有助于类风湿性关节炎(RA)和骨关节炎(OA)的研究和治疗，这两种疾病经常袭击这些关节。特别令人感兴趣的是用<；100μm分辨率对关节软骨进行成像，其完整性是疾病的主要指标。采用Talbot光栅干涉仪的基于相位差或折射的X射线成像(DPC)可以提供这样一种方法，因为它可以增强软组织对比度，并且可以用传统的X射线管来实现。首先开发了一个数字关节体模，以评估手持式DPC系统所需的角灵敏度和光谱。该模型预测，由于关节软组织的折射率非常相似，折射效应很小，需要很高的角分辨率。为了将我们的模型与实验进行比较，我们搭建了一台高分辨率的台式干涉仪，该干涉仪使用了10μm周期光栅、一个W阳极管和一个基于ccd的探测器。对动物软骨和人类手指的成像实验支持了该模型的预测。例如，在~25keV的平均能量下，软骨和水的折射率之间的估计差异只有几个百分点，可与线性衰减系数之间的差异相媲美。因此，DPC成像的潜在优势主要来自于软组织界面的边缘增强。使用身体人类手指的实验也与关节模型定性一致，表明折射对比由嵌入肌肉的肌腱主导，在我们的条件下很难观察到软骨层。然而，该模型预测，使用低能量的准单色光源，如K边过滤的Rh或Mo管，结合以高Talbot阶数运行的~2m长的对称干涉仪，用于手部小关节的DPC射线照相系统是可行的。
A high resolution radiographic method for soft tissues in the small joints of the hand would aid in the study and treatment of Rheumatoid Arthritis (RA) and Osteoarthritis (OA), which often attacks these joints. Of particular interest would be imaging with <100 μm resolution the joint cartilage, whose integrity is a main indicator of disease. Differential phase-contrast or refraction based X-ray imaging (DPC) with Talbot grating interferometers could provide such a method, since it enhances soft tissue contrast and it can be implemented with conventional X-ray tubes. A numerical joint phantom was first developed to assess the angular sensitivity and spectrum needed for a hand DPC system. The model predicts that due to quite similar refraction indexes for joint soft tissues, the refraction effects are very small, requiring high angular resolution. To compare our model to experiment we built a high resolution bench-top interferometer using 10 μm period gratings, a W anode tube and a CCD based detector. Imaging experiments on animal cartilage and on a human finger support the model predictions. For instance, the estimated difference between the index of refraction of cartilage and water is of only several percent at ~25 keV mean energy, comparable to that between the linear attenuation coefficients. The potential advantage of DPC imaging comes thus mainly from the edge enhancement at the soft tissue interfaces. Experiments using a cadaveric human finger are also qualitatively consistent with the joint model, showing that refraction contrast is dominated by tendon embedded in muscle, with the cartilage layer difficult to observe in our conditions. Nevertheless, the model predicts that a DPC radiographic system for the small hand joints of the hand could be feasible using a low energy quasi-monochromatic source, such as a K-edge filtered Rh or Mo tube, in conjunction with a ~2 m long ‘symmetric’ interferometer operated in a high Talbot order.
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