Lung segmentation and removal of PET spill-over activity artifacts. Semi-automated histogram segmentation and morphological region growing were used to delineate the set of lung voxels on the pre-treatment staging PET/CT studies. PET spill-over activities into the lung ROI were manually contoured for exclusion. Top row: lung ROI shown (a) before and (b) after manual correction of cardiac spill-over activity. Bottom row: the region of exclusion due to tumor is show in red (c) before and (d) after manual correction.