Longitudinal in vivo immuno-PET imaging of distribution of 124I-MORAb-004 in nude mice bearing subcutaneous chimeric ID8 tumor grafts over time. Mice were injected with 124I-MORAb-004 (5.2 MBq, 2.5 μg mAb) (A) or co-injected with 25 μg of unlabeled MORAb- 004 (B) and scanned for 1 h at different time points post-injection. Transverse projections from one mouse from each group in shown, with representative images of photon radiance from BLI of tumor grafts enriched with luciferase (fLuc)-transfected MS1 or MS1-TEM1 endothelial cells of respective mouse is shown to the left of each PET panel. (A) Increased uptake of 124I MORAb-004 was observed in tumors expressing TEM1+ tumor (right, white arrow), compared with control tumor (left, red arrowhead). (B) Specific blocking of 124I-MORAb-004 uptake in TEM1+ tumor observed following administration of excess unlabeled mAb.