An Improved Approach for Measurement of Regional Cerebral Rate Constants in the Deoxyglucose Method with Positron Emission Tomography

A new experimental approach was designed to measure regional rate constants for [18F]2-fluoro-2-d-deoxyglucose in the three-compartment model. A programmed infusion was used to keep the plasma tracer concentration constant for the first 20 min. Positron emission tomography images of the brain were taken every minute for 20 min in a low-resolution mode, then every 15–20 min for 2–3 h in a medium-resolution mode. Two simplified operational equations for the calculation of the regional rate constants were derived that incorporated the contribution of the vascular compartment to tissue activity. The first equation was applied to data collected during the initial 20 min (when the concentration of plasma tracer was constant) to estimate the values of k*1, k*2, k*3, and the fraction of the vascular compartment. The second equation was applied to data collected during the whole experimental period to find the value of k*4 and to provide a better estimate of k*3. The regional rate constants measured experimentally in three dogs and a brain tumor patient agreed well with those in the literature. This method permits estimation of the local CMRglu under pathological conditions using regionally measured rate constants and provides new information on the pathophysiological meaning of the rate constants.