【作者】 张鹏飞；

【导师】 田扬超；

【作者基本信息】 中国科学技术大学 ， 核科学与技术， 2016， 硕士

【摘要】 X射线相衬成像技术是近几年来X射线成像领域中的研究热点之一,轻元素构成的物质,如生物软组织等,对X射线的吸收能力较弱,传统的X射线吸收衬度成像不能很好地分辨这些物质,理论上,这些轻元素物质对X射线产生相移的相移截面比吸收截面高三个数量级,因此X射线相衬成像技术可以反映这些弱吸收物质的内部信息,可以大大地扩展了X射线成像的应用范围。围绕相衬成像技术发展出了多种获得相位图像的方法,在目前的众多相衬成像方法中,基于光栅相衬成像方法可以利用普通的X射线光源进行成像,不依赖于同步辐射光源或微焦点光源,并且可以通过所得的到的图像提取物体的吸收、相衬、散射三种信息,成为最有潜力应用于临床医疗和工业无损检测领域的成像技术。本论文主要基于中国科学技术大学同步辐射实验室的X射线光栅相衬成像装置进行成像实验,使用相位步进的方法获取样品的投影图像,并用信息分离方法来提取吸收、相衬和暗场的三种信息二维图像,在实际的实验工作中,X射线光源的不稳定性带来的光强漂移现象会影响信息提取的结果,进一步影响相衬成像的三维重建工作,因此本文中通过对相衬成像中相位步进曲线的研究,提出了修正光强漂移的方法,并利用实验验证了方法的正确性。在传统X射线成像中,计算机断层重建技术(CT)可以由多个角度下获得的投影图像来重建断层信息分布,实现无损检测的目的,而X射线相衬成像断层重建具有特殊性,本文介绍了CT重建算法的原理,并进行了数值模拟,然后推广到相衬成像CT重建中。本论文的最后提出了相衬成像研究中方便信息提取和重建研究的GUI软件框架,具有易用性、跨平台和可扩展性,可以为更进一步的相衬CT重建研究打下基础。更多还原

【Abstract】 X-ray phase imaging has attracted increasing attention during the past few decades, substance composed of light elements, such as biological soft tissue, which generate poor contrast by conventional x-ray absorbing imaging, Grating based phase constrast imaging with a Talbot-Lau interferometer could use conventional x-ray source instead of expensive synchrotron radiation (SR) source. Moreover, the phase-stepping data acquisition method in grating-based phase contrast imaging provides not only refraction images, but also absorbing images and small angle scatter signals. This method is fully compatible with existing computed tomography (CT) and can generate two additional images, which makes it one of the most potential technique applied in clinical practice and non-destructive testing.The thesis’experiment was carried out in the National Synchrotron Radiation Lab-oratory (NSRL) of the University of Science and Technology of China (USTC) using grating-based x-ray phase contrast imaging setup,we used phase-stepping technique to acquire data and data post-processing about information retrieval.In actual experiment, we found that the photon intensity drift of the x-ray source would influence the final images, especially the refraction images. After analyzing the phase-stepping curve, we proposed a correction method to fix the wrong image due to the effect of intensity drift. Experimental results showed the method could solve this problem and get the right re-sults successfully.In the conventional X-ray imaging, computed tomography technique (CT) can reconstruct the object’s cross-section detailed images with projections from a series of angles around axial direction. With CT technique, we can achieve the purpose of non-destructive testing, and X-ray phase contrast imaging tomographic has little dif-ference with conventional X-ray CT,in the thesis we explained the theories of CT re-construction and made numerical simulation about a phantom,then we discussed the CT reconstruction of phase contrast imaging.In the last part of the thesis we proposed a software framework with GUI about information retrieval and tomography reconstruction,featuring with ease of use, cross-platform and scalability. Then this framework can help us analysising data, furtherly lays a good foundation for future study about phase-contrast tomography.更多还原