Figure 10.

Standard deviation of the 65 mm diameter background ROI averaged over the ten slices surrounding the 15.9 mm cold sphere divided by the mean of the background ROI at the last iteration plotted versus the mean of the 15.9 mm diameter cold sphere divided by the mean of the background ROI at the last iteration as a function of iteration number. A curve closest to the origin represents the most desirable contrast-noise characteristics. The iteration number is increasing from 1 to 50 from right to left. (inset) A reconstruction of the cold sphere phantom. The larger circle represents the background ROI within the transaxial slice. The smaller circle represents the 10 mm ROI covering the 15.9 mm cold sphere.