Reconstruction results approaching convergence obtained for a sampling interval of 10°.

Columns from left to right show the reconstructed image, Log(RMSE), PSNR and UQI after two thousand iterations. Rows from top to bottom: images reconstructed using ART, 2-, 4-, and 8-directional gradient operators. As the same in Fig 5, even if the sampling interval is 10°, the gradient operators with more number of directions have better image quality.