Figure 4:

Axial CT image (512 × 512 pixels) from the test set labeled as “healthy.” (A–F) Images show the filtered back projection reconstruction from 2048, 1024, 512, 256, 128, and 64 views, respectively. (G–L) Images show the U-Net predictions of the respective images in the upper row, and (M–R) images show the results of the total variation (TV)–based method. The presented structural similarity index measure (SSIM) and peak signal-to-noise ratio (PSNR) values were calculated over the entire CT image scaled to [0–1] from the full Hounsfield unit range (−1024 to 3071 HU) with respect to the 4096-view reconstruction. All images are presented in the brain window ranging from 0 HU to 80 HU. The insert is 100 × 100 pixels; the entire image is 512 × 512 pixels.