X射线大视场相衬成像位移误差的数值分析
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摘要
随着X射线光栅相衬成像视场的扩大,相位步进法中的位移误差会对相衬图像造成很大影响.提出一种X射线大视场光栅相衬成像位移误差的数值分析方法,通过数值计算获得不同位移误差下两个聚苯乙烯小球的相衬成像结果.理论模型的数值计算结果表明,位移误差会导致小球相衬图像产生明暗条纹的背景干扰,位移误差越大,其相衬图像受背景条纹的干扰越严重.当位移误差达到光栅周期的1/10时,小球相衬信息几乎被背景条纹所淹没,致使其边缘信息无法识别.要获得背景均匀的大视场相衬图像,则位移误差最好控制在光栅周期的1/100以下.分析结果可为X射线大视场相衬成像系统的设计提供参考依据.
With the expansion of field of view(FOV) in grating-based X-ray phase-contrast imaging(XPCI),shift error in phase stepping method causes a great impact on the quality of phase-contrast image. A method is presented to analyze shift error in grating-based XPCI for large FOV,and the imaging results of two polystyrene spheres under different shift errors are obtained by numerical calculation. The results show that interferences of strip patterns appear in the background of phase-contrast images. The larger the shift error is,the more serious the interference becomes.When the shift error is up to 1 /10 of the grating period,the edges of the spheres are unable to be identified from strip patterns. And shift error has to be set as less than 1 /100 of the grating period to obtain a phase-contrast image without strip patterns for large FOV. The numerical analysis and discussion of shift error will be beneficial to the design of grating-based XPCI for large of view.
With the expansion of field of view(FOV) in grating-based X-ray phase-contrast imaging(XPCI),shift error in phase stepping method causes a great impact on the quality of phase-contrast image. A method is presented to analyze shift error in grating-based XPCI for large FOV,and the imaging results of two polystyrene spheres under different shift errors are obtained by numerical calculation. The results show that interferences of strip patterns appear in the background of phase-contrast images. The larger the shift error is,the more serious the interference becomes.When the shift error is up to 1 /10 of the grating period,the edges of the spheres are unable to be identified from strip patterns. And shift error has to be set as less than 1 /100 of the grating period to obtain a phase-contrast image without strip patterns for large FOV. The numerical analysis and discussion of shift error will be beneficial to the design of grating-based XPCI for large of view.
引文
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[27]Vincent R,Christian K,Rolf K,et al.Noise analysis of grating-based X-ray differential phase contrast imaging[J].Review of Scientific Instruments,2010,81:073709.
[2]Donath T,Pfeiffer F,Bunk O,et al.Phase-contrast imaging and tomography at 60 ke V using a conventional X-ray tube source[J].Review of Scientific Instruments,2009,80:053701.
[3]Herzen J,Donath T,Pfeiffer F,et al.Quantitative phasecontrast tomography of a liquid phantom using a conventional X-ray tube source[J].Optics Express,2009,17(12):10010-10018.
[4]Stampanoni M,Wang Z,Thuring T,et al.The first analysis and clinical evaluation of native breast tissue using differential phase-contrast mammography[J].Investigative Radiology,2011,46(12):801-806.
[5]Kottler C,David C,Pfeiffer F,et al.A two-directional approach for grating based differential phase contrast imaging using hard X-rays[J].Optics Express,2007,15(3):1175-1181.
[6]Bonse U,Hart M.An X-ray interferometer[J].Applied Physics Letters,1965,6(8):155-156.
[7]Davis T J,Gao D,Gureyev T E,et al.Phase-contrast imaging of weakly absorbing materials using hard X-rays[J].Nature,1995,373:595-598.
[8]Wilkins S W,Gureyev T E,Gao D,et al.Phase-contrast imaging using polychromatic hard X-rays[J].Nature,1996,384(6607):335-338.
[9]David C,N9hammer B,Solak H H,et al.Differential Xray phase contrast imaging using a shearing interferometer[J].Applied Physics Letters,2002,81(17):3287-3289.
[10]Pfeiffer F,Weitkamp T,Bunk O,et al.Phase retrieval and differential phase-contrast imaging with low-brilliance X-ray sources[J].Nature Physics,2006,2:258-261.
[11]Tannka J,Nagashima M,Kido K,et al.Cadaveric and in vivo human joint imaging based on differential phase contrast by X-ray Talbot-Lau interferometry[J].Zeitschrift Für Medizinische Physik,2012,23(3):222-227.
[12]Momose A,Yashiro W,Kido K,et al.X-ray phase imaging:from synchrotron to hospital[J].Philosophical Transactions A:Mathematical Physical and Engineering Sciences,2014,372(2010):20130023.
[13]Tapfer A,Bech M,Pauwels B,et al.Development of a prototype gantry system for preclinical X-ray phase-contrast computed tomography[J].Medical Physics,2011,38(11):5910-5915.
[14]Tapfer A,Bech M,Velroyen A,et al.Experimental results from a preclinical X-ray phase-contrast CT scanner[J].Proceedings of the Nation Academy of Sciences of the United States of America,2012,109(39):15691-15696.
[15]Zambelli J,Bevins N,Qi Z,et al.Radiation dose efficiency comparison between differential phase contrast CT and conventional CT[J].Medical Physics,2010,37(6):2473-2479.
[16]Revol V,Kottler C,Kaufmann R,et al.X-ray interferometer with bent gratings:towards larger fields of view[J].Nuclear Instruments and Methods in Physics Research A:Accelerators,Spectrometers,Detectors and Associated Equipment,2011,648(S1):S302-S305.
[17]Weber T,Bayer F,Haas W,et al.Energy-dependent visibility measurements,their simulation and optimisation of an X-ray Talbot-Lau interferometer[J].Journal of Instrumentation,2012,7(11):1313-1218.
[18]Huang Jianheng,Lei Yaohu,Du Yang,et al.Quantitative analysis of fringe visibility in grating-based X-ray phasecontrast imaging[J].Journal of the Optical Society of America A:Optics,Image Science,and Vision,2016,33(1):69-73.
[19]Liu X,Guo J C,Lei Y H,et al.Two-step phase retrieval method with unknown phase shift on non-absorbtion grating X-ray differential phase contrast imaging system[J].Nuclear Instruments and Methods in Physics Research A:Accelerators,Spectrometers,Detectors and Associated Equipment,2012,691:86-89.
[20]Lei Yaohu,Du Yang,Li Ji,et al.Application of Bi absorption gratings in grating-based X-ray phase contrast imaging[J].Applied Physics Express,2013,6(11):117301.
[21]Xi Yan,Zhao Jun.Inner-focusing reconstruction method for grating-based phase-contrast CT[J].Optics Express,2013,21(5):6224-6232.
[22]刘鑫,郭金川.部分相干光源微分相衬双图像相位恢复[J].深圳大学学报理工版,2014,31(2):169-173.Liu Xin,Guo Jinchuan.Dual-images phase retrieval in differential phase-contrast imaging with partial coherence source[J].Journal of Shenzhen University Science and Engineering,2014,31(2):169-173.(in Chinese)
[23]李新斌,陈志强,张丽,等.基于X射线光栅相衬成像的乳腺癌诊断技术的现状和发展前景[J].中国体视学与图像分析,2015,20(4):305-318.Li Xinbin,Chen Zhiqiang,Zhang Li,et al.The status and development prospect of the diagnosis of breast cancer based on grating-based X-ray phase-contrast imaging[J].Chinese Journal of Stereology and Image Analysis,2015,20(24):305-318.(in Chinese)
[24]雷耀虎,刘鑫,郭金川,等.超声对X射线分析光栅铋填充率影响研究[J].深圳大学学报理工版,2016,33(2):138-142.Lei Yaohu,Liu Xin,Guo Jinchuan,et al.Influence of ultrasonic on filling ratio of Bi in X-ray analyzer gratings[J].Journal of Shenzhen University Science and Engineering,2016,33(2):138-142.(in Chinese)
[25]Wang Shenghao,Olbinado M P,Momose A,et al.Experimental research on the feature of an X-ray Talbot-Lau interferometer versus tube accelerating voltage[J].Chinese Physics B,2015,24(6):673-678.
[26]黄建衡,杜杨,雷耀虎,等.硬X射线微分相衬成像的噪声特性分析[J].物理学报,2014,63(16):168702.Huang Jianheng,Du Yang,Lei Yaohu,et al.Noise analysis of hard X-ray differential phase contrast imaging[J].Acta Physica Sinica,2014,63(16):168702.(in Chinese)
[27]Vincent R,Christian K,Rolf K,et al.Noise analysis of grating-based X-ray differential phase contrast imaging[J].Review of Scientific Instruments,2010,81:073709.