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FIGURE 3. Localization of a micrometastatic human colon cancer cell line disseminated in lungs of nude mice using small-animal PET. Necropsy data showed all animals with 
80 to 120 tumor nodules in lungs, ranging in size from a few cells to colonies that were <0.3 mm in diameter. (A) Activity is seen in lungs of coronal section 1.5 h after anti-CEA pretargeted 124I-hapten-peptide injection. Additionally, uptake was seen in kidneys (Kid) due to peptide clearance through this organ and stomach (Stom) as a result of catabolized iodide. (B) A tumor-bearing animal given only 124I-hapten peptide without bs-mAb showed no selective uptake in chest. In this slice, activity is also seen in kidneys, stomach, and urinary bladder (UB). (C) Transverse section through the chest shows uptake, with appearance of individual nodules (arrows). (D) Autoradiography study was performed in separate animals pretargeted with an 111In-labeled peptide at a later time after tumor implantation, but, even in these animals, individual tumor nodules did not exceed 0.5 mm. Autoradiography revealed selective uptake in and around tumor nodules within lungs.
