Cerebral glucose metabolism

Abstract

Glucose is the main substrate for energy metabolism of the brain, and the regional cerebral metabolic rate is directly related to regional brain activity. Therefore, the measurement of regional glucose metabolism is of great importance for the assessment of regional normal function and of pathological changes. Quantitation of glucose metabolism by PET is based on the 2-deoxyglucose method developed by Sokoloff and colleagues: F18-labelled deoxyglucose (FDG) is transported into the brain and phosphorylated, but cannot be further metabolised and therefore is accumulated intracellularly. The concentration of the tracer can be measured three dimensionally by PET, and together with the arterial tracer concentration, the kinetics of glucose uptake can be assessed, and the regional cerebral metabolic rates for glucose (rCMRGlc) can be calculated. rCMRGlc is high in cortex and grey matter structures and low in white matter, but there are significant differences among various regions. Metabolic rate is slightly reduced with ageing and changed by sleep, dream, and functional activation. CMRGlc is significantly affected in pathological states, and the regional and global changes are important for assessing the severity of disorders and for differential diagnosis of diseases of the brain. Therefore, FDG-PET has still great importance in brain research and many applications in clinical neurology.