X射线光栅相位衬度成像实验技术和应用研究

发布时间：2017-12-26 22:20

本文关键词：X射线光栅相位衬度成像实验技术和应用研究　出处：《中国科学技术大学》2017年博士论文　论文类型：学位论文

【摘要】：近二十年来,X射线相衬成像得到快速发展,形成了若干种方法。大部分X射线相衬成像方法需要高空间或时间相干性光源,因此都局限于同步辐射或者微焦点光源。然而,光栅相衬成像能够使用大功率的常规X光管作为光源,并且兼容大视场的平板探测器,给X射线相衬成像应用于临床和工业带来曙光。另外,光栅相衬成像能同时得到吸收、折射和散射三种相互补充的衬度信息,提供了传统吸收成像无法探测的信息。经过全世界大量科学家的努力,X射线光栅相衬成像已经取得了巨大的发展,在许多应用领域进行了尝试。特别是在医学成像方面,大量的预临床实验取得了令人鼓舞的结果,吸引了越来越多科学界和工业界的关注和投入。本论文围绕光栅相衬成像这一热点方向,在搭建的光栅相衬成像系统的基础上,对X射线光栅相衬成像的实验技术进行了深入地探索;针对系统出现的问题,对光源、光栅和探测器这些核心部件进行了检测和优化,分析了问题并提出了相应的校正和改进方案;通过实际实验,对光栅相衬成像方法在生物医学成像和食品检测等应用进行了初步探索。这些工作将大大地促进光栅相衬成像技术的广泛应用。本论文的研究成果归纳如下:1.光栅相衬成像装置实验技术:前期完成了基于几何投影的非相干光栅相衬成像系统的搭建,总结了一套完整精细的光栅相衬成像实验技术和数据处理流程;最后通过性能测试比较本系统和传统Talbot-Lau干涉仪,指出了本系统的特点。2.X光源的光强偏移现象及校正方法:发现了提前折射信息错误现象,进而分析了光强漂移对实验结果的影响。分析光强随时间的变化的规律,利用线性的拟合获得光强的解析表达式,再基于位移曲线提出了一种光强漂移的校正方法,并利用光栅相衬成像实验验证了该方法的有效性。3.吸收光栅优化放置的成像系统:为了减小光栅的热振动和损伤,基于光栅结构和材料的特点,分析并比较了正入射和背入射两种光栅放置方案。计算和实验表明两种方案在成像结果上一致,但背入射能减小相应的热效应带来的光栅振动乃至变形,提高系统的稳定性,延长光栅使用寿命。4.改进的光栅相衬成像探测器校正方案:为了简化现有探测器校正过程中的复杂操作,提出了一种将源光栅和光源作为一个整体参与增益校正的探测器校正方法,并通过实验验证了方案的可行性。进一步从理论上分析了暗电流和增益校正对三个信息的影响,提出了一种只需要暗电流校正的光栅相衬成像探测器图像校正方法。实验表明新方案和现有方法成像效果一致,并且能大幅度的简化实验操作过程,提高工作效率和系统稳定性。5.生物医学成像和食品检测等应用探索:提出了一种结合吸收和折射的新型骨密度测量方案并通过理论计算和实验得到了验证;基于鲫鱼的光栅相衬成像结果,发现并验证了不同的样品处理方法对相衬成像实验结果的影响;最后,以常见的黄梅干和圣女果作为样品,探索了相衬成像在食品检测方面的潜力。
[Abstract]:In the past twenty years, X - ray phase contrast imaging has developed rapidly, and several methods have been formed. Most of the X - ray phase contrast imaging methods require high spatial or temporal coherent light sources, so they are limited to synchrotron radiation or microfocus light sources. However, grating phase contrast imaging can be used as a source of high-power conventional X light source, and compatible with large field of view detector. It brings dawn to X and phase contrast imaging in clinical and industrial applications. In addition, the grating phase contrast imaging can simultaneously obtain three complementary contrast information of absorption, refraction and scattering, which provides information that can not be detected by traditional absorption imaging. Through the efforts of a large number of scientists all over the world, the X - ray grating phase contrast imaging has made great progress and has been tried in many fields of application. In particular, a large number of pre clinical trials have yielded encouraging results in medical imaging, attracting more and more attention and input from the scientific and industrial communities. This paper focuses on grating imaging on this hot topic, based on grating imaging system is built on the in-depth exploration of experimental technology of X X-ray grating imaging; aiming at the problem of the system and the detection and optimization of light source, grating and detector of these core components, analyzes the problems and puts forward the correction and the corresponding improvement scheme; through practical experiments, the method of phase contrast imaging grating in biomedical imaging and food detection and other applications are explored. These work will greatly promote the wide application of grating phase contrast imaging technology. The research results of this thesis are summarized as follows: 1. grating imaging device: the complete set of experimental techniques based on geometrical projection non coherent grating imaging system, summed up a complete set of fine grating imaging technique and data processing; finally, through the comparison of the performance test system and the traditional Talbot-Lau interferometer, pointed out the characteristics of this system. The phenomenon of light intensity migration and correction of 2.X light source: the error of early refraction information is found, and the influence of light intensity drift on the experimental results is analyzed. The rule of light intensity changing with time is analyzed, and the analytical expression of light intensity is obtained by linear fitting. Then a correction method of intensity drift based on displacement curve is put forward, and the effectiveness of the method is verified by grating phase contrast imaging experiment. 3. absorption grating optimized placement of imaging system: in order to reduce the thermal vibration and damage of grating, based on the characteristics of grating structure and material, two kinds of grating placement schemes of normal incidence and back incidence were analyzed and compared. The calculation and experiment show that the two schemes are consistent in the imaging results, but the back incident can reduce the grating vibration and deformation caused by the corresponding thermal effects, improve the stability of the system and prolong the service life of the grating. Grating imaging detector 4. improved calibration scheme: in order to simplify the complex operation of the existing detector calibration process, a grating and light source as a whole in the detector gain correction correction method, and the feasibility of the scheme is verified by experiment. Further, the influence of dark current and gain correction on three information is further analyzed theoretically. A new correction method of grating phase contrast imaging detector is proposed, which only needs dark current correction. The experiment shows that the new scheme is consistent with the existing methods, and can greatly simplify the operation process and improve the efficiency and stability of the system. 5. biomedical imaging and food detection application: a new type of bone mineral density measurement method combining absorption and refraction and through the theoretical calculation and experimental verified; grating imaging results based on crucian carp, found and verified in the sample processing method on the experimental results of different phase contrast imaging; finally, in common Huangmei and Cherry Tomatoes as the sample, to explore the phase contrast imaging in food detection potential.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O434.19

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