基于校正靶特征与Biharmonic样条插值的XRⅡ图像扭曲校正
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摘要
针对扭曲的XRII图像给C臂X光机成像系统实时标定带来不利影响的问题,提出了基于校正靶特征和Biharmonic样条曲面插值相结合的XRⅡ图像扭曲校正方法.在分析校正靶自身特征的基础上,使用Otsu算法与形态学相结合的方法提取了校正靶网格线交叉点坐标,然后拟合提取出的网格线交叉点坐标,最后使用Biharmonic样条曲面插值方法校正扭曲的XRII图像.实验结果表明,使用由Otsu算法与形态学相结合的方法提取的校正靶网格线交叉点坐标值与理想校正靶网格线交叉点坐标值的残留误差和标准误差分别为10.489 0±0.074 0和4.263 2±0.015 0,然而使用Biharmonic样条曲面插值校正之后残留误差和标准误差分别降低至(7.121 85±3.354 15)×10-13和(3.915 1±1.862 7)×10-13.
To solve the problem that distortional XRⅡ(X-ray image intensifier) image brings about adverse effect on real time calibration for C-arm CT(computer tomography) imaging system,a distortion correction method for XRII image based on calibration grid characteristic and Biharmonic spline surface interpolation is proposed.After analysing calibration grid characteristic,a connection method of Otsu algorithm and morphology is proposed to extract the coordinates of intersect marker on calibration grid.Then the extracted coordinates are used to fit a surface.Finally,Biharmonic spline surface interpolation are used to correct the distorted XRII image.Experiment demonstrates that the residual error and the standard error between the extracted intersect marker coordinates on calibration grid using Otsu algorithm and morphology and the intersect marker coordinates on calibration grid of ideal image are 10.489 0±0.074 0 and 4.263 2±0.015 0,respectively.However,after using Biharmonic spline surface interpolation,the residual error and the standard error are respectively reduced to(7.121 85±3.354 15)×10-13 and(3.915 1±1.862 7)×10-13.
To solve the problem that distortional XRⅡ(X-ray image intensifier) image brings about adverse effect on real time calibration for C-arm CT(computer tomography) imaging system,a distortion correction method for XRII image based on calibration grid characteristic and Biharmonic spline surface interpolation is proposed.After analysing calibration grid characteristic,a connection method of Otsu algorithm and morphology is proposed to extract the coordinates of intersect marker on calibration grid.Then the extracted coordinates are used to fit a surface.Finally,Biharmonic spline surface interpolation are used to correct the distorted XRII image.Experiment demonstrates that the residual error and the standard error between the extracted intersect marker coordinates on calibration grid using Otsu algorithm and morphology and the intersect marker coordinates on calibration grid of ideal image are 10.489 0±0.074 0 and 4.263 2±0.015 0,respectively.However,after using Biharmonic spline surface interpolation,the residual error and the standard error are respectively reduced to(7.121 85±3.354 15)×10-13 and(3.915 1±1.862 7)×10-13.
引文
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[2]Gutierrez L F,Ozturk C,McVeigh E R,et al.A practi-cal global distortion correction method for an image inten-sifier based X-ray fluoroscopy system[J].Med Phys,2008,35(3):997-1007.
[3]Yan S J,Wang C T,Ye M.A method based on movingleast squares for XRII image distortion correction[J].Med Phys,2007,34(11):4194-4206.
[4]Habets D F,Pollmann S I,Yuan X H,et al.Error anal-ysis of marker-based object localization using a single-plane XRII[J].Med Phys,2009,36(1):190-200.
[5]李颖超,王涌天,杨健.基于像素运动模型的数字造影系统成像畸变校正[J].电子学报,2008,36(8):1473-1479.Li Yingchao,Wang Yongtian,Yang Jian.Distortion cor-rection based on pixel-movement model in angiographysystem[J].Acta Electronica Sinica,2008,36(8):1473-1479.(in Chinese)
[6]Sandwell D T.Biharmonic spline interpolation of GEOS-3SEASAT altimeter data.geophysical[J].Research Let-ters,1987,14(2):139-142.
[7]夏吉庄.双调和样条内插方法在测井和地震资料整合中的应用[J].石油与天然气地质,2010,31(2):244-249.Xia Jizhuang.An application of biharmonic spline inter-polation to integration of logging and seismic data[J].Oil&Gas Geology,2010,31(2):244-249.(in Chi-nese)
[8]王亚涛,董兰芳,倪奎.基于Biharmonic样条插值的图像渐变算法及实现[J].中国图象图形学报,2007,12(12):2190-2194.Wang Yatao,Dong Lanfang,Ni Kui.Image morphing al-gorithm based on Biharmonic interpolation and its imple-mentation[J].Journal of Image and Graphics,2007,12(12):2190-2194.(in Chinese)
[9]Sund T,Eilertsen K.An algorithm for fast adaptive im-age binarization with applications in radiotherapy imaging[J].IEEE Transactions on Medical Imaging,2003,22(1):22-28.
[10]Castleman K R.数字图像处理[M].朱志刚,等译.北京:电子工业出版社,2011.
[11]闫士举,王成焘,钱理为.基于Hough变换和连通体分析的混合圆形体检测算法[J].自动化学报,2008,34(4):408-413.Yan Shiju,Wang Chengtao,Qian Liwei.A hybrid ap-proach based hough transform and connected componentanalysis for circular objects detection and measurement[J].Acta Automatica Sinica,2008,34(4):409-413.(in Chinese)
[12]Chung K L,Huang H L,Chen I C.New two-phase spa-tial data structures with applications to binary images[J].Journal of Visual Communication and Image Rep-resentation,2003,14(2):97-113.
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