Fig. 2.

A gray-scale white light image of an exposed subcutaneous xenograph glioma tumor grown on the left flank of an athymic mouse is depicted in (a). Targeted and untargeted tracer uptakes at 2 min after tracer injection are presented in (b) and (c), respectively. The pixel-based normalization approach, wherein all untargeted tracer images are scaled by a normalization factor map that is determined by dividing, pixel-by-pixel, the uptake images of the targeted and untargeted tracers at 2-min post-injection, is depicted in (d). The reference tissue-based normalization approach, wherein all untargeted tracer images are scaled by a single normalization factor determined by the ratio of the uptakes of the targeted and untargeted tracers in a region devoid of receptor is depicted in (e).