Regional cerebral function determined by FDG-PET in healthy volunteers: normal patterns and changes with age

The main objective of this study was to determine patterns of regional brain metabolic activity utilizing high-resolution PET in normal healthy volunteers and variations in different age groups.

High-resolution [18F]FDG PET images of the entire brain were obtained in 120 healthy normal volunteers (64 men, 56 women), age range from 19 to 79 yr. Each anatomic region was assessed using a qualitative rating scale with a score ranging from 1 to 6 (1 = definitely normal and 6 = definitely abnormal). Local metabolic activity was also estimated as showing increased (+) or decreased (-) compared to normal (0) states.

The most consistent finding in normal aging was decreased cortical metabolism, particularly in the frontal lobes. Temporal, parietal and occipital lobe metabolism varied considerably among subjects within the same age group as well as over decades. Basal ganglia, hippocampal area, thalami, cerebellum, posterior cingulate gyrus and visual cortex remained metabolically unchanged with advancing age.

These data indicate that qualitative interpretation of FDG-PET images allows accurate assessment of regional metabolic activity of the brain in normal subjects similar to those described with quantitative techniques. Adequate knowledge of normal variations and changes related to normal aging is necessary for optimal assessment of pathologic states.