Resting brain metabolic activity in a 4 tesla magnetic field

MRI is a major tool for mapping brain function; thus it is important to ass ess potential effects on brain neuronal activity attributable to the requis ite static magnetic field. This study used positron emission tomography (PE T) and F-18-deoxyglucose ((18)FDG) to measure brain glucose metabolism (a m easure of brain function) in 12 subjects while their heads were in a 4 T MR I field during the (18)FDG uptake period. The results were compared with th ose obtained when the subjects were in the earth's field (PET scanner), and when they were in a simulated MRI environment in the PET instrument that i mitated the restricted visual field of the MRI experiment. Whole-brain meta bolism, as well as metabolism in occipital cortex and posterior cingulate g yrus, was lower in the real (4 T) and simulated (0 T) MRI environments comp ared with the PET. This suggests that the metabolic differences are due mai nly to the visual field differences characteristic of the MRI and PET instr uments. We conclude that a static magnetic field of 4 T does not in itself affect this fairly sensitive measure of brain activity. (C) 2000 Wiley-Liss , Inc.