Modified Grangeat algorithm as apply to a circular scan orbit

[1] Feldkamp, Davis L A, Kress J. Practical cone-beam algorithm[J]. Journal of the Optical Society of America, 1984, 1(1):1612-619 [2] Grangeat P. Mathematical framework of cone beam 3D reconstruction via the first derivative of the Radon transform Louis A K,Natterer F. Mathematical Methods in Tomography. Herman GT: Springer Verlag, 1991:66-97 [3] Lee Seung Wook, Cho Gyuseong, Wang Ge. Artifacts associated with implementation of the Grangeat formula[J]．Med Phys, 2002, 29(12):2871-2880 [4] 曾凯,陈志强,张丽,等.圆轨道锥束重建精度与锥角关系的研究[J].CT理论与应用研究, 2003,12(3):9-16 Zeng Kai, Chen Zhiqiang, Zhang Li, et al. The study of relationship between circular orbit cone beam reconstruction error and cone angle[J]. CT Theory and Applications, 2003,12(3):9-16(in Chinese) [5] Chen Zhiqiang, Li Liang, Kang Kejun, et al. New developments of exact cone-beam CT reconstruction algorithms[J]. CT Theory and Applications, 2005,14(3):65-70 [6] Marr R B, Chen C N, lauterbur P C．On two approaches to 3D reconstruction in NMR zeugmatography Natterer F. Mathematical Aspects of Computerized Tomography. Herman GT: Springer Verlag, 1981:225-240