Methodologic factors affecting PET measurements of cerebral glucose metabolism

Measurements of cerebral glucose utilization rates in similar populations of human subjects under similar conditions vary considerably because of methods used in data collection and analysis. Using data acquired in two patients, we evaluated the effects of time schedule of data collection, region of interest size, method of attenuation correction, and input function shape on LCMRglu determined by dynamic positron emission tomographic scanning and calculation of rate constants. These different strategies of data acquisition and analysis produced variations of 3 to 14% in calculated LCMRglu. These factors, in conjunction with the well described effects of instrument resolution and sensitivity may account for data discrepancies in the literature.