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

• Published in: European journal of nuclear medicine and molecular imaging Vol. 38; no. 10; pp. 1876 - 1886
• Main Authors: Zhao, Songji, Kuge, Yuji, Yi, Min, Zhao, Yan, Hatano, Toshiyuki, Magota, Keiichi, Nishijima, Ken-ichi, Kohanawa, Masashi, Tamaki, Nagara
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01.10.2011
• Subjects: Animals; Cardiology; Diagnosis, Differential; Granuloma - diagnostic imaging; Granuloma - pathology; Imaging; Male; Medicine; Medicine & Public Health; Methionine; Neoplasms - diagnostic imaging; Neoplasms - pathology; Nuclear Medicine; Oncology; Original Article; Orthopedics; Positron-Emission Tomography; Radiology; Rats; Rats, Wistar; Granuloma; Tumor; Dynamic; C-MET PET; Inflammation; Rat
• ISSN: 1619-7070; 1619-7089
• DOI: 10.1007/s00259-011-1865-2

Purpose We evaluated whether the dynamic profile of L - 11 C-methionine ( 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). 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 11 C-MET PET was performed by small animal PET up to 120 min after injection of 11 C-MET. The next day, after overnight fasting, the rats were injected with 18 F-2-deoxy-2-fluoro- D -glucose ( 18 F-FDG), and dynamic 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. Results 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 11 C-MET uptake in the granuloma was significantly different from that in the tumor ( p  < 0.001). In the static analysis of 11 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 18 F-FDG in the granuloma were similar to those in the tumor ( p  = NS). Conclusion Dynamic 11 C-MET PET has an additional value for differentiating malignant tumors from granulomatous lesions, which deserves further elucidation in clinical settings.