免分析光栅一次曝光相位衬度成像方法

X射线光栅微分相位衬度成像技术可以观察到常规吸收衬度成像难以分辨的弱吸收物质的精细结构信息,因而在医学、材料学等研究领域具有巨大的应用前景.但传统的X射线光栅微分相位衬度成像技术由于采用分析光栅作为空间滤波器,需要采用相位步进法扫描分析光栅来获得样品的多张投影图像才能够分离出样品的吸收、折射和散射信息,因此存在样品曝光时间长、辐射剂量高以及X射线光通量利用率低等问题,限制了其在各个学科领域的应用研究.为克服上述问题,本文提出一种基于免分析光栅相位衬度成像系统的一次曝光样品信息提取算法.该算法只需要利用一块相位光栅,进而采用高分辨探测器进行样品投影数据的一次采集即可提取样品的吸收、折射和散射信息.理论和模拟研究结果表明:与传统相位步进法相比,该算法具有样品信息提取精度高,且不受光栅的自成像周期需为探测器像素尺寸的整数倍条件的限制.此外,该算法还能够有效地减少对生物样品的辐射损伤,因此在生物医学成像等研究领域中具有广泛的应用前景.

Method of single exposure phase contrast imaging without analyser grating

X-ray differential phase contrast imaging technology can reveal the weakly absorbing fine structure which cannot be observed by the conventional X-ray absorption contrast imaging.Hence,it has potential applications in many fields such as medical science,and material science.But in the traditional X-ray grating differential phase contrast imaging system,the analyser grating is used as a spatial filter,and needs to be phase stepped,then multiple exposures are required for information extraction.Thus this leads to high-dose radiation exposure and low efficiency of X-ray utilization.All these disadvantages limit its application in various disciplines.In order to cope with the above issues,a new algorithm based on single-shot grating differential phase contrast imaging system without analyzer grating is proposed.In such a system the absorption,refraction and scattering information can be obtained from one projective image of the sample acquired by a high-resolution detector.The reliability of this new algorithm is confirmed by numerical simulation.Compared with the phase stepping algorithm,the proposed algorithm can provide very accurate and reliable information extraction results without requiring the grating period to match with detector pixel size.It facilitates the reduction of the radiation damage to sample.We emphasize that this method is highly compatible with the future X-ray phase contrast imaging clinical applications.