Reverse projection retrieval in edge illumination x-ray phase contrast computed tomography
Reverse projection retrieval in edge illumination x-ray phase contrast computed tomography
复制标题
DOI：
10.1088/0022-3727/49/25/255501
复制
发表时间：
2016-05
期刊：
影响因子：
--
通讯作者：
C. Hagen;M. Endrizzi;P. Diemoz;A. Olivo
中科院分区：
文献类型：
--
作者：
C. Hagen;M. Endrizzi;P. Diemoz;A. Olivo
边缘照明（EI）x射线相衬计算机断层扫描（CT）可以提供样品的复折射率（n=1−δ+iβ）的真实的实部和虚部的三维分布。相位恢复，即从包含两者的组合的投影中分离衰减和折射数据，是图像重建过程中的关键步骤。在基于EI的X射线相衬CT中，这通常是基于在每个CT角度处以相反的照射配置（即，具有预采样掩模的不同位置）采集的两个投影来执行的。在每个投影处移动预采样掩模使得扫描容易受到电机引起的未对准的影响，并防止连续的样本旋转。我们提出了一种替代方法，用于检索衰减和折射数据，不需要重新定位的前样本掩模。该方法基于Zhu等人（2010 Proc. Natl Acad. Sci. USA 107 13576-81）用于基于光栅干涉的X射线相衬CT。我们使用这种关系，以获得一个简化的采集策略，允许采集数据与连续的样品旋转，这可以减少扫描时间时，结合快速读出检测器。除了讨论的理论和必要的实验装置的对齐，我们提出的断层图像与反向投影检索，并证明他们的协议与传统的EI检索。
Edge illumination (EI) x-ray phase contrast computed tomography (CT) can provide three-dimensional distributions of the real and imaginary parts of the complex refractive index (n=1−δ+iβ) of the sample. Phase retrieval, i.e. the separation of attenuation and refraction data from projections that contain a combination of both, is a key step in the image reconstruction process. In EI-based x-ray phase contrast CT, this is conventionally performed on the basis of two projections acquired in opposite illumination configurations (i.e. with different positions of the pre-sample mask) at each CT angle. Displacing the pre-sample mask at each projection makes the scan susceptible to motor-induced misalignment and prevents a continuous sample rotation. We present an alternative method for the retrieval of attenuation and refraction data that does not require repositioning the pre-sample mask. The method is based on the reverse projection relation published by Zhu et al (2010 Proc. Natl Acad. Sci. USA 107 13576–81) for grating interferometry-based x-ray phase contrast CT. We use this relation to derive a simplified acquisition strategy that allows acquiring data with a continuous sample rotation, which can reduce scan time when combined with a fast read-out detector. Besides discussing the theory and the necessary alignment of the experimental setup, we present tomograms obtained with reverse projection retrieval and demonstrate their agreement with those obtained with the conventional EI retrieval.