Comparison of Cerebral Glucose Metabolic Rates Measured with Fluorodeoxyglucose and Glucose Labeled in the 1, 2, 3–4, and 6 Positions Using Double Label Quantitative Digital Autoradiography

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Abstract
We compared local cerebral glucose metabolic rates (LCMRglu) that were determined with [18F]fluorodeoxyglucose (FDG) and [14C]glucose labeled in the 1, 2, 3–4, and 6 positions. Double label digital autoradiography was used with published kinetic models to determine LCMRglu for FDG and glucose in the same animals. Glucose showed metabolic rate dependent underestimation of LCMRglu compared to FDG, which worsened with increasing experimental times. The least underestimation occurred with glucose labeled in the 6 position at 6 min, reaching 10% in areas of high metabolism. Labeling in the 1 position, the 2 position and the 3–4 position caused progressively worse underestimation at all times. In addition, some structures showed differences not directly related to metabolic rate, indicating regional variations in relationships between individual kinetic constants of FDG and glucose.