EVALUATION OF 2 POPULATION-BASED INPUT FUNCTIONS FOR QUANTITATIVE NEUROLOGICAL FDG PET STUDIES

The conventional measurement of the regional cerebral metabolic rate o f glucose (rCMRGlc) with fluorodeoxyglucose (FDG) and positron emissio n tomography (PET) requires arterial or arterialised-venous (a-v) bloo d sampling at frequent intervals to obtain the plasma input function ( IF). We evaluated the accuracy of rCMRGlc measurements using populatio n-based IFs that were calibrated with two a-v blood samples. Populatio n based Ifs were derived from: (1) the average of a-v Ifs from 26 pati ents (Standard IF) and (2) a published model of FDG plasma concentrati on (Feng IF). Values for rCMRGlc calculated from the population-based Ifs were compared with values obtained with Ifs derived from frequent a-v blood sampling in 20 non-diabetic and six diabetic patients. Value s for rCMRGlc calculated with the different Ifs were highly correlated for both patient groups (r greater than or equal to 0.992) and root m ean square residuals about the regression line were less than 0.24 mg/ min/100 g, The Feng IF tended to underestimate high rCMRGlc. Both popu lation-based Ifs simplify the measurement of rCMRGlc with minimal loss in accuracy and require only two a-v blood samples for calibration. T he reduced blood sampling requirements markedly reduce radiation expos ure to the blood sampler.