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

Purpose: We evaluated whether the dynamic profile of L-C-methionine (C-MET) may have an additional value in differentiating malignant tumors from granulomas in experimental rat models by small animal positron emission tomography (PET). Methods: 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 C-MET PET was performed by small animal PET up to 120 min after injection of C-MET. The next day, after overnight fasting, the rats were injected with F-2-deoxy-2-fluoro- D-glucose (F-FDG), and dynamic 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. Results: 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 C-MET uptake in the granuloma was significantly different from that in the tumor ( p < 0.001). In the static analysis of C-MET, visual assessment and SUV analysis could not differentiate the tumor from the granuloma in all cases, although the mean SUV in the granuloma (1.48 ± 0.09) was significantly lower than that in the tumor (1.72 ± 0.18, p < 0.01). The dynamic patterns, static images, and mean SUVs of F-FDG in the granuloma were similar to those in the tumor ( p = NS). Conclusion: Dynamic C-MET PET has an additional value for differentiating malignant tumors from granulomatous lesions, which deserves further elucidation in clinical settings. [ABSTRACT FROM AUTHOR]