Determination of regional rate constants from dynamic FDG-PET studies in Parkinson's disease

Dynamic [18F]fluorodeoxyglucose (FDG) PET was used in Parkinson's disease patients and normal controls to determine kinetic rate constants for FDG. The goal was to assess whether the metabolic decreases observed in Parkinson's disease are associated with transport or phosphorylation processes or both.

Fluorine-18-FDG was administered to 18 Parkinson's disease and 15 normal control subjects. Dynamic PET scanning was performed for 1 h and rate constants were obtained by nonlinear, least-squares analysis. Regional glucose metabolic rate was calculated from the individually fitted rate constants and by two standard static scan analyses.

Global CMRglu was decreased in Parkinson's disease (mean reduction 22%), reaching statistical significance in all regions investigated. K1 was significantly reduced in parietal cortex, temporal cortex and striatum while k3 was significantly reduced only in parietal cortex. The rate constant k2 was unchanged.

K1, k3 and CMRglu all demonstrated greater deficits across the brain with progression of disease and development of dementia, particularly in the parietal an occipital cortex. This suggested that the metabolic disturbance may be a global dysfunction throughout the brain. Because altered rate constants are specifically taken into account, dynamic measurements has shown to provide higher sensitivity for detecting diminished glucose utilization in Parkinson's disease than static approaches.