title: Dynamic 11C-methionine PET analysis has an additional value for differentiating malignant tumors from granulomas: an experimental study using small animal PET.
abstract: OBJECTIVE
  We evaluated whether the dynamic profile of L-(11)C-methionine (11C-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 11C-MET PET was performed by small animal PET up to 120 min after injection of 11C-MET. The next day, after overnight fasting, the rats were injected with 18F-2-deoxy-2-fluoro-D-glucose (18F-FDG), and dynamic 18F-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
  11C-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 11C-MET uptake in the granuloma was significantly different from that in the tumor (p<0.001). In the static analysis of 11C-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 18F-FDG in the granuloma were similar to those in the tumor (p=NS).
  
  
  CONCLUSIONS
  Dynamic 11C-MET PET has an additional value for differentiating malignant tumors from granulomatous lesions, which deserves further elucidation in clinical settings.
authors: Department of Nuclear Medicine, Graduate School of Medicine, Hokkaido University, Sapporo, Japan.
authors: Songji
authors: S
authors: Zhao
authors: Yuji
authors: Y
authors: Kuge
authors: Min
authors: M
authors: Yi
authors: Yan
authors: Y
authors: Zhao
authors: Toshiyuki
authors: T
authors: Hatano
authors: Keiichi
authors: K
authors: Magota
authors: Ken-ichi
authors: K
authors: Nishijima
authors: Masashi
authors: M
authors: Kohanawa
authors: Nagara
authors: N
authors: Tamaki
mesh_terms: D000818:Animals; D003937:Diagnosis, Differential; D006099:Granuloma / Q000000981:diagnostic imaging* / Q000473:pathology; D008297:Male; D008715:Methionine; D009369:Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D049268:Positron-Emission Tomography; D051381:Rats; D017208:Rats, Wistar
chemical_list: C086242:carbon-11 methionine; D008715:Methionine