We compared the contributions of the labeled tracers (11)C-methionine (Met) and (18)F-FDG for PET-guided stereotactic biopsy of brain gliomas.
METHODS: In 32 patients with glioma, stereotactic Met PET and (18)F-FDG PET were integrated in the planning of stereotactic brain biopsy. PET images were analyzed to determine which tracer offered the best information for target definition. The stereotactic coregistration of PET images allowed accurate comparison of the level, distribution, and extent of uptake for both tracers according to tumor location and grade.
RESULTS: A histologic diagnosis was obtained for all patients. All gliomas had an area of abnormal Met uptake, and 27 showed abnormal (18)F-FDG uptake. (18)F-FDG was used for target selection when its uptake was higher in tumor than in gray matter (14 gliomas). Seven were in the basal ganglia or brain stem. Met was used for target selection when there was no (18)F-FDG uptake or when (18)F-FDG uptake was equivalent to that in the gray matter (18 gliomas). Thirteen were in the cortex. Sixty-one of the 70 stereotactic trajectories obtained from the 32 patients were based on PET-defined targets and had an area of abnormal Met uptake. These 61 Met-positive trajectories always yielded a diagnosis of tumor. All nondiagnostic trajectories (n = 9) were obtained in areas with no increased uptake of Met. In all patients with increased uptake of both tracers, the focus of highest Met uptake corresponded to the focus of highest (18)F-FDG uptake. However, the extent of uptake of both tracers was variable.
CONCLUSION: Distributions of highest Met and (18)F-FDG uptake are similar in brain gliomas. Because Met provides a more sensitive signal, it is the molecule of choice for single-tracer PET-guided neurosurgical procedures in gliomas.