Reconstruction results of an abdomen image by using EPTV combined with the multi-directional gradient operators when the sampling interval is 5°.

First row: ground truth; subsequent rows from top to bottom: images reconstructed using EPTV combined with the 3-, 6-, and 26-directional gradient operators, respectively. Images from left to right show the sagittal, transaxial, and coronal sections of the abdomen. Areas marked by dotted rectangles are enlarged and displayed in Fig 13. Subsequent rows from top to bottom, the lower images in the figure, the smoother they are, and are closer to the original images.