Wu Zhao, Gao Kun, Wang Zhili, Wang Shengxiang, Zhu Peiping, Ren Yuqi, Tian Yangchao
National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei, Anhui 230029, People's Republic of China.
School of Electronic Science and Applied Physics, Hefei University of Technology, Hefei, Anhui 230009, People's Republic of China.
J Synchrotron Radiat. 2021 May 1;28(Pt 3):854-863. doi: 10.1107/S1600577521001806. Epub 2021 Mar 12.
The reverse projection protocol results in fast phase-contrast imaging thanks to its compatibility with conventional computed-tomography scanning. Many researchers have proposed variants. However, all these reverse projection methods in grating-based phase-contrast imaging are built on the hypothesis of the synchronous phase of reference shifting curves in the whole field of view. The hypothesis imposes uniformity and alignment requirements on the gratings, thus the field of view is generally limited. In this paper, a generalized reverse projection method is presented analytically for the case of non-uniform reference in grating-based phase tomography. The method is demonstrated by theoretical derivation, numerical simulations and synchrotron radiation experiments. The influence of imaging position to sensitivity, and the phase-wrapping phenomenon are also discussed. The proposed method combines the advantages of the high efficiency of the reverse projection method and the universal applicability of the phase-stepping method. The authors believe that the method would be used widely in fast and dose-constrained imaging.
由于其与传统计算机断层扫描的兼容性，反向投影协议可实现快速相衬成像。许多研究人员提出了变体。然而，基于光栅的相衬成像中的所有这些反向投影方法都是基于整个视场中参考移位曲线同步相位的假设构建的。该假设对光栅提出了均匀性和对准要求，因此视场通常受到限制。本文针对基于光栅的相断层扫描中参考不均匀的情况，解析地提出了一种广义反向投影方法。通过理论推导、数值模拟和同步辐射实验对该方法进行了验证。还讨论了成像位置对灵敏度的影响以及相位包裹现象。所提出的方法结合了反向投影方法的高效率和相移方法的普遍适用性的优点。作者认为该方法将在快速和剂量受限成像中得到广泛应用。
