Dynamic ^sup 11^C-methionine PET analysis has an additional value for differentiating malignant tumors from granulomas: an experimental study using small animal PET

We evaluated whether the dynamic profile of L-^sup 11^C-methionine (^sup 11^C-MET) may have an additional value in differentiating malignant tumors from granulomas in experimental rat models by small animal positron emission tomography (PET). Rhodococcus aurantiacus and allogenic rat C6 glioma cells were inoculated, respectively, into the right and left calf muscles to generate a rat model bearing both granulomas and tumors (n=6). Ten days after the inoculations, dynamic ^sup 11^C-MET PET was performed by small animal PET up to 120 min after injection of ^sup 11^C-MET. The next day, after overnight fasting, the rats were injected with ^sup 18^F-2-deoxy-2-fluoro-D-glucose (^sup 18^F-FDG), and dynamic ^sup 18^F-FDG PET was performed up to 180 min. The time-activity curves, static images, and mean standardized uptake value (SUV) in the lesions were calculated. ^sup 11^C-MET uptake in the granuloma showed a slow exponential clearance after an initial distribution, while the uptake in the tumor gradually increased with time. The dynamic pattern of ^sup 11^C-MET uptake in the granuloma was significantly different from that in the tumor (p