Fig. 7

The reconstruction results of the Shepp–Logan phantom. a–d The image reconstructed by L1-DL, ADSIR, GPBB and SART respectively with 60 scanning views data simulated by 2 million photons; e–h the difference between the reconstructed image (a–d) and the original image (OI); i–l the image reconstructed by L1-DL, ADSIR, GPBB and SART respectively with 60 scanning views data simulated by 1 million photons; m–p the difference between the reconstructed image (i–l) and the original image (OI)