X射线光栅相位衬度成像技术研究

发布时间：2018-04-15 02:19

本文选题：X射线 + 光(?)相位衬度成像　；参考：《中国科学技术大学》2017年硕士论文

【摘要】：X射线应用广泛,在临床医学、材料科学及国土安全等领域占有重要地位。为了实现对轻元素组成物质的检测,X射线相位衬度成像应运而生,近二十年来得到了迅速的发展,相继开展了多种X射线相位衬度成像技术的研究。X射线光栅相位衬度成像技术的出现,不再对光源有严格要求,能在常规X光源上实现折射信息的提取,有临床应用的可能,因此获得了广泛的关注,关于该技术的研究迅速展开。针对X射线光栅相衬成像技术,本论文主要在光栅相位衬度成像实验平台的搭建、光栅的研制及相位衬度成像方法的研究方面开展了以下工作:1.X射线光栅相位衬度成像实验平台的搭建和图像采集系统的优化搭建X射线光栅相位衬度成像实验平台,该成像装置将传统的Talbot-Lau干涉仪和几何投影成像原理结合在一起。主要有以下几个优点:光栅制作容易,有利于实现高剂量的相位衬度成像;成像装置设计更紧凑,对成像系统的机械稳定性要求低;成像能量选择更多,应用范围更广。通过Labview编程,将实验时所需要的操作整合到一个界面上,我们可以同时实现对X射线光源参数的设置,对光栅位移运动的操作,图像采集和图像后处理,方便实验人员操作,减少了实验时间。在图像采集方面,我们介绍了一种名为积分水桶法的图像采集方法,对比传统的相位步进法,它的主要优点有:分析光栅连续移动,这种连续运动的方式有利于成像系统的机械的稳定性;X射线探测器连续采集图像,减少了样品接受到的不必要的辐射。2.X射线光栅相位衬度成像重要部件光栅的制作作为X射线光栅相位衬度成像的重要部件,光栅的质量对成像结果有决定性的作用。在制作大高宽比光栅的过程中,经常会出现光栅结构失效的问题。针对这个问题,我们在光栅制作工艺上提出改进方案,可以逐步制作出满足成像要求的大高宽比光栅。3.X射线光栅相位衬度成像背景校正方法的研究通过对目前常用的两种背景校正方法的对比研究,发现在背景图像存在较大的不均匀性时,其中一种方法会出现错误。针对这个问题,我们在该方法的基础上提出了优化方案,在相位步进过程中采用循环移位寻找正确的起始位置,对原有的方法进行了优化。最后,模拟分析和实验数据证实该方法可行且正确。
[Abstract]:X-ray is widely used and plays an important role in clinical medicine, material science and homeland security.In order to realize the detection of light element composition matter, X-ray phase contrast imaging emerged as the times require, and it has been developed rapidly in the past twenty years.Many kinds of X-ray phase contrast imaging techniques have been carried out one after another. The appearance of X-ray grating phase contrast imaging technology is no longer strictly required to the light source, and it can be used to extract refraction information on the conventional X light source, which has the possibility of clinical application.Therefore, wide attention has been paid to the research of this technology.Aiming at the phase contrast imaging technology of X-ray grating, this paper mainly builds the experimental platform of grating phase contrast imaging.The development of grating and the research of phase contrast imaging method have carried out the following work: 1. Build the experimental platform of X-ray grating phase contrast imaging and optimize the image acquisition system to build the experimental platform of X-ray grating phase contrast imaging.The imaging device combines the traditional Talbot-Lau interferometer with the geometric projection imaging principle.The main advantages are as follows: the grating is easy to fabricate, which is conducive to the realization of high dose phase contrast imaging; the imaging device is designed more compact and requires low mechanical stability of the imaging system; the imaging energy is more selective, and the range of application is wider.Through Labview programming, the operation needed in experiment can be integrated into a single interface. We can set the parameters of X-ray light source at the same time, operate the movement of grating displacement, capture images and post-process images, and facilitate the operation of the experimenter.The experiment time is reduced.In the aspect of image acquisition, we introduce an image acquisition method called integral bucket method. Compared with the traditional phase step method, its main advantages are: analyzing the continuous movement of grating,This mode of continuous motion is conducive to the mechanical stability of the imaging system and the continuous acquisition of images by X-ray detectors.The unnecessary radiation received by the sample is reduced. 2. The fabrication of the grating as an important part of the X-ray grating phase contrast imaging is an important part of the X-ray grating phase contrast imaging. The quality of the grating plays a decisive role in the imaging results.In the process of fabricating large aspect ratio gratings, the structural failure of gratings often occurs.In order to solve this problem, we put forward the improvement scheme in grating fabrication technology.The background Correction method of Phase contrast Imaging with large aspect ratio grating .3.The background Correction method of Phase contrast Imaging based on X-ray grating can be made step by step. The comparison of two kinds of background correction methods commonly used at present can be carried out.It is found that there are errors in one of the methods when there is a large heterogeneity in the background image.In order to solve this problem, we put forward an optimization scheme based on this method. In the process of phase step, we use cyclic shift to find the correct starting position, and optimize the original method.Finally, the simulation analysis and experimental data show that the method is feasible and correct.
【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O434.1;TP391.41

【参考文献】