一种新的TR层析扫描投影重排算法
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摘要
TR层析扫描可对超出射束范围的大尺寸构件进行检测,在工业CT领域有着重要的应用。目前使用的一种重建方法是在忽略扇角的影响下,将TR扫描正弦图直接重排成标准平行束正弦图,然后使用平行束的重建方法进行重建,这样导致重建图像存在一定误差。提出一种新的重排算法,通过坐标转换和插值计算,得到平行束正弦图中的各采样点在TR扫描正弦图中对应的映射点坐标及灰度信息,进而得到完整的平行束正弦图。通过仿真和试验,发现应用新算法得到的正弦图和重建图像均消除了边缘不光滑和伪影现象。新的重排算法能够消除现有重排算法的误差,使得TR扫描方法在扇束角较大时也能实现正确CT重建。
TR tomographic scanning can detect large-scale components beyond the beam range, and has important applications in the field of ICT. One of the current reconstruction methods is to directly rebinding TR scan sinogram into standard parallel-beam sinogram without considering the influence of sector angle, and then reconstruct them using parallel-beam reconstruction method, which results in some errors in the reconstructed images. In this paper, a new rebinding algorithm is proposed. Through the coordinate transformation and interpolation calculation, the coordinates and gray scale information of the corresponding mapping points of the sampling points in the parallel sinogram are obtained in the TR scan sinogram. In this way, a complete parallel beam sinogram is obtained. Through simulations and experiments, it is found that the edge smoothness and artifacts are eliminated in both the sinogram and the reconstructed image obtained by the improved algorithm. The new rebinding algorithm can eliminate the errors of the existing rebinding algorithm. The TR scanning method can also achieve correct CT reconstruction when the fan beam angle is large.
TR tomographic scanning can detect large-scale components beyond the beam range, and has important applications in the field of ICT. One of the current reconstruction methods is to directly rebinding TR scan sinogram into standard parallel-beam sinogram without considering the influence of sector angle, and then reconstruct them using parallel-beam reconstruction method, which results in some errors in the reconstructed images. In this paper, a new rebinding algorithm is proposed. Through the coordinate transformation and interpolation calculation, the coordinates and gray scale information of the corresponding mapping points of the sampling points in the parallel sinogram are obtained in the TR scan sinogram. In this way, a complete parallel beam sinogram is obtained. Through simulations and experiments, it is found that the edge smoothness and artifacts are eliminated in both the sinogram and the reconstructed image obtained by the improved algorithm. The new rebinding algorithm can eliminate the errors of the existing rebinding algorithm. The TR scanning method can also achieve correct CT reconstruction when the fan beam angle is large.
引文
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[2]负明凯,刘力.数字实时成像(DR)与X射线胶片成像对比分析[J].CT理论与应用研究,2005,14(3):13-17.YUN Mingkai,LIU Li.Comparative analysis of digital real-time imaging(DR)and X-ray film imaging[J].CT Theory and Application,2005,14(3):13-17.
[3]孙永玲.射线无损检测发展趋向[J].无损检测,1996(11):328-330.SUN Yongling.Development trend of radiation nondestructive testing[J].Nondestructive Testing,1996(11):328-330.
[4]王侃.产品工业CT扫描重建模型与CAD模型比对技术的研究与实现[D].重庆:重庆大学,2012.WANG Kan.Research and implementation of the comparing technology between CTscanning reconstruction model and CAD model for product industry[D].Chongqing:Chongqing University,2012.
[5]倪培君,蔡和平,任安峰,等.基于组分特性的材料密度工业X射线CT定量检测[J].无损检测,2011,33(7):5-10.NI Peij un,CAI Heping,REN Anfeng,et al.Quantitative detection of material density by industrial X-ray CT based on component characteristics[J].Nondestructive Testing,2011,33(7):5-10.
[6]杜乙,王贤刚,向新程.一种用于CT偏置扫描重建的指数型加权函数[J].清华大学学报(自然科学版),2015,55(1):115-121.DU Yi,WANG Xiangang,XIANG Xincheng.An exponential weighting function for CT offset scanning reconstruction[J].Journal of Tsinghua University(Natural Science Edition),2015,55(1):115-121.
[7]周光湖.计算机断层摄影原理及应用[M].成都:成都电讯工程学院出版社,1986.ZHOU Guanghu.Principles and applications of computed tomography[M].Chengdu:Chengdu Telecommunications Engineering Institute Press,1986.
[8]王增勇,汤光平,李建文,等.工业CT技术进展及应用[J].无损检测,2010,32(7):504-508.WANG Zengyong,TANG Guangping,LI Jianwen,et al.Progress and application of industrial CT technology[J]. Nondestructive Testing,2010,32(7):504-508.
[9]毛小渊.二维CT图像重建算法研究[D].南昌:南昌航空大学,2016.MAO Xiaoyuan.Research on twodimensional CT image reconstruction algorithm[D].Nanchang:Nanchang Hangkong University,2016.
[10]王露衡.第二代CT卷积反投影重建算法的研究及三种CT扫描方式的仿真[D].重庆:重庆大学,2000.WANG Luheng.Research on the second generation CT convolution back proj ection reconstruction algorithm and simulation of three CT scanning methods[D].Chongqing:Chongqing University,2000.
[11]叶海霞.工业CT窄角扇束卷积反投影并行图像重建研究[D].重庆:重庆大学,2003.YE Haixia.Research on parallel image reconstruction of industrial CT narrow-angle fan beam convolution back proj ection[D].Chongqing:Chongqing University,2003.
[12]蒋阳.基于WINDOWS'98窄扇束角扫描CT图像系统实用化研究[D].重庆:重庆大学,2000.JIANG Yang.Practical research on CT image system based on WINDOWS'98 narrow fan beam angle scanning[D].Chongqing:Chongqing University,2000.
[13]庄天戈.CT算法与原理[M].上海:上海交通大学出版社,1992.ZHUANG Tiange.CT algorithm and principle[M].Shanghai:Shanghai Jiaotong University Press,1992.
[14]谢强.计算机断层成像技术一原理,设计,伪像和进展[M].北京:科学出版社,2006.XIE Qiang.Computed tomographyprinciples,design,artifacts and progress[M].Beijing:Science Press,2006.
[15]NOO F,DEFRISE M,CL ACKDOYLE R,et al.Image reconstruction from fan-beam projections on less than a short scan[J].Physics in Medicine and Biology,2002,47(14):2525-2 546.
[16]傅健,路宏年.一种新颖的ICT扫描方式及其FBP重构算法[J].北京航空航天大学学报,2003,29(1):9-12.FU Jian,LU Hongnian.A novel ICT scanning method and its FBP reconstruction algorithm[J].Journal of Beijing University of Aeronautics and Astronautics,2003,29(1):9-12.
[17]PHONG B T.Illumination for computer generated pictures[J].Communications of the ACM,1975,18(6):311-317.
[18]HERMAN G T,Image reconstruction from projection:the fundamentals of computed tomography[M].New York:Academic Press,1980.