PET findings in lymphomatosis and gliomatosis of the brain: a comparison of C-11 methionine PET/CT and F-18 FDG PET/CT.

Background: Positron emission tomography (PET) findings for gliomatosis and lymphomatosis have been rarely reported.

Objective: To compare PET/computed tomography (CT) findings using 11C-methionine (MET) from PET/CT findings using 18F-fluorodeoxy glucose (FDG) for patients with lymphomatosis or gliomatosis of the brain.

Methods: Participants comprised all 10 patients with lymphomatosis or gliomatosis of the brain treated at our institution in the past 12 years. Underlying pathologies comprised intravascular lymphoma (n = 1), lymphomatosis (n = 3), and gliomatosis (n = 6). All cases were pathologically diagnosed. In seven patients, both MET-PET/CT and FDG-PET/CT were performed simultaneously in a single study. In three patients, only FDG-PET/CT was performed. The degree of tracer accumulation to the lesion was evaluated qualitatively. Quantitatively, the ratio of maximum standard uptake value (SUVmax) in tumor to that in normal tissue (T/N ratio) was measured and compared between FDG and MET.

Results: Qualitatively, MET accumulated to part of the lesion in six of seven patients and almost all of the lesion in one in seven patients. FDG accumulated to part of the lesion in three of ten patients and almost all of the lesion in one of ten patients. No FDG accumulation was seen in the lesion in six patients. Quantitatively, mean ± SD T/N ratio was significantly higher with MET (2.11 ± 0.63) than with FDG (1.18 ± 0.84; P < 0.05, Wilcoxon signed-rank test).

Conclusions: In lymphomatosis and gliomatosis, FDG accumulates in only part of the lesion. FDG is thus less suitable than MET for depicting these lesions.