Segmentation variations by 5% difference in threshold values. (A) Multiple PET axial image slices from a rabbit with an active lung infection are shown for demonstration purpose (color code: cold). Areas of light color indicate higher PET intensities, while areas of darker color signify background, noise, or uptake belonging to minimum metabolism. (B) Two locally adaptive threshold levels outline areas of interesting uptake regions. Here, only a 5% difference in thresholding level is shown by green and red (i.e., pink outline is the inner boundaries of red outline), respectively.