Fig. 1. Imaging geometry of helical cone-beam CT.螺旋锥束CT成像几何

Fig. 2. Imaging geometry of circular fan beam CT.圆轨迹扇束CT成像几何

Fig. 3. Reconstruction planes and virtual filtering lines in helical cone beam CT geometry.螺旋锥束CT几何中的待重建平面和虚拟滤波线

Fig. 4. Imaging geometry of single reconstruction plane.单个待重建平面螺旋锥束成像几何

Fig. 5. Imaging schematic for local volume: (a) Side view; (b) top view.局部体区域成像示意图　(a)侧视图; (b)俯视图

Fig. 6. Reconstruction image without truncation: (a), (b), (c) True value; (d), (e), (f) helical FDK algorithm; (g), (h), (i) the proposed algorithm.无截断投影重建图像　(a), (b), (c)真值; (d), (e), (f)螺旋FDK算法; (g), (h), (i)本文算法

Fig. 7. Plots of reconstruction image without truncated projections: (a), (b), (c) the vertical plots of the first, second, and third column slices of Fig.6., respectively. 无截断投影重建图像剖线图　(a), (b), (c)分别为图6第一列、第二列和第三列切片的垂直剖线

Fig. 8. Reconstruction image without truncated projections: (a), (b), (c) With helical FDK algorithm; (d), (e), (f) the proposed algorithm.带噪声无截断投影重建图像　(a), (b), (c)螺旋FDK算法; (d), (e), (f)本文算法

Fig. 9. Local reconstruction results for the Popeye phantom: (a) Without the truncated projection data, the helical FDK algoritm; (b) without the truncated projection data, the proposed algorithm; (c) with the truncated projection data, the helical FDK algoritm; (d) with the truncated projection data, the proposed algorithm.Popeye体模局部成像实验结果　(a)无截断投影数据, 螺旋FDK算法; (b)无截断投影数据, 本文算法; (c)有截断投影数据, 螺旋FDK算法; (d)有截断投影数据, 本文算法