Simplified PET quantitation of myocardial glucose utilization.

Unlabelled: The purpose of this study was to validate experimentally a simple method to quantify tissue glucose utilization with the brain reference index (BRI) using 14C-deoxyglucose and assess its clinical feasibility for myocardial PET.

Methods: To validate the BRI method, glucose utilization in myocardial and skeletal muscle was studied in rats with 14C-deoxyglucose after increasing doses of oral glucose loading. To assess clinical feasibility of the method, the BRI was applied to nine patients undergoing myocardial PET and compared to rMGU measured by the deoxyglucose model of Sokoloff et al. and by Patlak graphical analysis. The normal range of myocardial FDG uptake expressed as the BRI was estimated with four normal volunteers.

Results: In skeletal muscle, a dose-dependent increase of glucose utilization was observed during oral glucose loading with doses up to 4 mg/g. In the myocardium, glucose utilization increased with a glucose loading dose of up to 1 mg/g without increasing further at greater glucose doses. Ratios of maximal glucose utilization in glucose-loaded rats to 19-hr fasted rats (controls), expressed as the BRI for left and right ventricular myocardium and skeletal muscle were 4.16, 3.74 and 7.39, respectively. Glucose utilization of right ventricular myocardium was approximately 70% of left ventricular myocardium for all glucose-loaded conditions. For patients, the BRI correlated with rMGU; four of these patients had a constant plasma glucose concentration.

Conclusion: Myocardial BRI is a sensitive indicator of rMGU that does not require dynamic data acquisition or constant plasma glucose concentrations.