EFFECTS OF HYPERGLYCEMIA ON FDG UPTAKE IN HUMAN BRAIN AND GLIOMA

This study evaluates the effects of hyperglycemia on fluorodeoxyglucos e (FDG) uptake in the human brain and in brain tumors. Methods: We per formed glucose loading during FDG PET studies in nine patients with br ain tumors (eight gliomas and one brain metastasis) and one with resec ted glioma. Two FDG PET scans were obtained in all cases within 1 wk i n a control state and with glucose loading by intravenous infusion of 10% glucose solution. Serial arterial blood sampling was performed in all cases to obtain fractional uptake of FDG normalized by the plasma integral uptake of radioactivity (FU). Results: In all nine patients w ith brain tumors, the tumor was depicted more clearly with glucose loa ding than in the control state. Glucose loading decreased FU in the ce rebral cortex (54.2% +/- 13.8%) nearly in inverse proportion to the pl asma glucose level, while the tumors showed a decrease (42.5% +/- 15.6 %), resulting in an increased tumor-to-cortex ratio by 26.0% +/- 5.7%. Fractional uptake in the cerebellum, white matter and the edematous a rea also decreased by glucose loading (53.9% +/- 13.2%, 49.6% +/- 10.3 % and 34.9% +/- 9.6%, respectively). Conclusion: These results demonst rate the different effects of hyperglycemia on normal brain tissue and on tumor, suggesting that glucose loading may be a valuable adjunct t o FDG PET to enhance detection of recurrent or residual brain tumors