代数迭代重建算法在折射衬度CT中的应用

X射线折射衬度CT是一种基于相位衬度的断层成像技术，特别适合对由轻元素组成的生物、医学样品进行成像，可以观察到常规吸收衬度CT无法观察到的软组织内部微细结构，是一种具有巨大发展潜力的新成像方法.迭代重建算法和解析重建算法是计算机断层成像技术中并行发展的两种算法，虽然已经提出了几种X射线折射衬度CT的解析重建算法，可是还未见X射线折射衬度CT迭代重建算法的报道.研究了代数迭代重建算法在X射线折射衬度CT中的应用，比较分析了不同的投影数据排列方式对于折射衬度CT重建图像的影响，并对实验数据进行了图像重建，获得了满意的CT图像.研究结果表明，在相位衬度CT中，迭代重建算法相对于解析重建算法而言，能减少投影次数，降低曝光剂量，减少对生物样品的辐射损伤，在生物样品成像和投影数据不完整的情况下具有明显的优势. 关键词： 衍射增强成像 代数迭代算法 CT重建 同步辐射

The application of algebraic reconstruction techniques in X-ray refraction contrast CT

X-ray refraction contrast CT is the computer tomography based on phase contrast. When the biological samples are taken from organs or tissues，X-ray refraction contrast CT provides more internal subtle details compared with conventional absorption CT images and it is considered a novel and very promising imaging technique. The iterative and analytical algorithms are the two main strategies in computer tomography. In the field of X-ray refraction contrast CT several analytical algorithms have been reported in the past. However the algorithm using iterative method have not been proposed. In this study，we tested the application of iterative algorithm in X-ray refraction contrast CT image reconstruction，investigated the influence of the order in which data are accessed in algebraic reconstruction techniques，and satisfactory CT images were obtained. Our data demonstrated that when biological samples are imaged or the complete projective data are not available，our iterative algorithm showed significant advantage over the analytical algorithms. It effectively reduces the number of the projection data，exposure time，as well as the radiation damage to the biology samples.