Alternative Approach to Single-Scan Estimation of Cerebral Glucose Metabolic Rate Using Glucose Analogs, with Particular Application to Ischemia

In the glucose analog method for determining local glucose utilization rates, time courses of tissue and plasma radioactivity are measured and then analyzed in terms of first-order exchange of label between tissue compartments. The rate of glucose utilization is assumed to have a fixed, linear relationship to the analog phosphorylation rate calculated from the fitted rate constants. Accurate estimation of the rate constants requires many hours of dynamic data acquisition. Therefore, techniques assuming a linear relationship between analog phosphorylation rate and total tissue concentration of label were developed to predict glucose utilization rates from a single scan. Previously reported linearizations differ in their sensitivity to differences between current and average kinetic rate constants, and thus in their accuracy. We have developed a method that is insensitive to the presumed value of the blood flow–capillary wall transport parameter k1. This new single-scan approach has been validated by comparison of the single-scan metabolic rate values with the values calculated from the dynamic measurements.