Lian S, Yang H, Kudo H, Momose A, Yashiro W
Midorino Research Corporation, 5-15-13 Chuo Rinkan Nishi, Yamato, Kanagawa 242-0008, Japan.
Division of Information Engineering, Faculty of Engineering, Information and Systems, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, Ibaraki 305-8573, Japan.
Rev Sci Instrum. 2015 Feb;86(2):023707. doi: 10.1063/1.4908139.
The X-ray phase imaging method has been applied to observe soft biological tissues, and it is possible to image the soft tissues by using the benefit of the so-called "Talbot effect" by an X-ray grating. One type of the X-ray phase imaging method was reported by combining an X-ray imaging microscope equipped by a Fresnel zone plate with a phase grating. Using the fringe scanning technique, a high-precision phase shift image could be obtained by displacing the grating step by step and measuring dozens of sample images. The number of the images was selected to reduce the error caused by the non-sinusoidal component of the Talbot self-image at the imaging plane. A larger number suppressed the error more but increased radiation exposure and required higher mechanical stability of equipment. In this paper, we analyze the approximation error of fringe scanning technique for the X-ray microscopy which uses just one grating and proposes an improved algorithm. We compute the approximation error by iteration and substitute that into the process of reconstruction of phase shift. This procedure will suppress the error even with few sample images. The results of simulation experiments show that the precision of phase shift image reconstructed by the proposed algorithm with 4 sample images is almost the same as that reconstructed by the conventional algorithm with 40 sample images. We also have succeeded in the experiment with real data.
X射线相位成像方法已被应用于观察柔软的生物组织，利用X射线光栅的所谓“塔尔博特效应”可以对软组织进行成像。一种X射线相位成像方法是通过将配备菲涅耳波带片的X射线成像显微镜与相位光栅相结合来实现的。使用条纹扫描技术，通过逐步移动光栅并测量数十个样品图像，可以获得高精度的相移图像。选择图像数量是为了减少成像平面上塔尔博特自成像的非正弦分量所引起的误差。图像数量越多，误差抑制效果越好，但会增加辐射剂量并要求设备具有更高的机械稳定性。在本文中，我们分析了仅使用一个光栅的X射线显微镜条纹扫描技术的近似误差，并提出了一种改进算法。我们通过迭代计算近似误差，并将其代入相移重建过程中。即使样本图像数量很少，该过程也能抑制误差。模拟实验结果表明，所提算法利用4个样本图像重建的相移图像精度与传统算法利用40个样本图像重建的相移图像精度几乎相同。我们还利用真实数据成功完成了实验。
