Figure 13.

A 65 mm diameter background ROI was placed over 5 slices free of rods and spheres. The STD of the background ROI divided by the mean of the background ROI at the last iteration plotted versus the mean of the 31.8 mm diameter cold sphere divided by the mean of the background ROI at the last iteration as a function of iteration number is shown. A curve closest to the origin represents the most desirable contrast-noise characteristics. The iteration number is increasing from 1 to 40 from right to left. (inset) A reconstruction after 15 iterations. The small circle shows the 20 mm ROI covering the 31.8 mm cold sphere.