Age and Gender Dependency of Cerebral and Cerebellar Glucose Metabolism

1. BackgroundKnowledge of gender-related changes in cerebral and cerebellar glucose metabolism in healthy adults is an important factor for differentiation between pathological and physiological brain conditions. We aimed to test the practical applicability of a commercially available, semi-automated program for cerebral segmentation ofthe uptake of PET tracers hypothesizing an age-dependent decline in FDG uptake metrics by PET/CT imaging. 2. Method Forty-two healthy subjects, 15 women (57.8±10.9 years) and 27 men (50.1±16.2 years) underwent FDG PET/CT as part of a prospective study. Scans were acquired 180 min. post tracer injection (4 MBq/kg) and analyzed using ROVER™ software. FDG uptake metrics were reported in standardized uptake value per body weight (SUV). The brain was divided into 4 volumes of interest: left and right cerebral hemispheres(Ce_L and Ce_R) and left and right cerebellar hemispheres (Cb_L and Cb_R). Each volume of interest was segmented using liver SUVmean as the lower threshold within each subject. For each hemisphere, the following variables were recorded: Volume, SUVmean, SUVmean-total, SUVmax, SUVpeak and partial volume corrected SUVmean-total.3. Results Qualitative analysis confirmed the negative correlation between volume and age in cerebral hemispheres (Ce_L: rho = -0.33, p = 0.03; Ce_R: rho = -0.41, p = 0.01). The SUVmean values of cerebral hemispheres also decreased significantly with increasing age (Ce_L: rho = -0.31, Ce_R: rho = -0.31, p = 0.04). Volume andSUVmean of the cerebellar hemispheres did not significantly associate with age. There was also a significant age-related loss of SUVmean-total in both cerebral hemispheres. The average SUVmean-total decline per age decade in cerebral area was more rapid in females than males: Ce_L, Female: -7%, Male: -4%; Ce_R, Female:-7%, Male: -5%. Healthy men had significantly higher volumetric values in the four brain regions, without meaningful higher metabolic activity, p < 0.05. 4. ConclusionsUsing ROVER software, which was easily applicable, we found a significant age-related decline in volume, SUVmean, and SUVmean-total in cerebral hemispheres, but not cerebellar hemispheres. All male hemispheres were larger than corresponding female hemispheres both in cerebral and cerebellar regions. We did not find a significant gender difference in cerebral and cerebellar glucose metabolism.