In vivo measurement of glucose utilization in rats using a beta-microprobe: direct comparison with autoradiography.

A new beta-microprobe (betaP) has been used to locally measure the time-concentration curve of a radiolabeled substance. The betaP, analogous to positron emission tomography methodology, is useful for in vivo animal studies because it can acquire time-concentration curves with high temporal and spatial resolution. Using [18F]fluoro-2-deoxy-D-glucose and betaP, we evaluated the reliability of the biologic parameters and we compared this method with the [14C]2-deoxy-D-glucose autoradiography. BetaP time-concentration curves in three regions of the brain were obtained from 24 rats. Four kinetic parameters (K1-k4) were estimated from 60-minute experimental periods using a three-compartment model. Best fits were obtained when the vascular fraction (Fv) was estimated simultaneously with the four kinetic parameters (K1-k4). The mean estimated Fv values were about 5.5% for the frontal cortex regions and 8.0% for the cerebellum. Correlation coefficients higher than 0.830 were observed between regional cerebral metabolic rates for glucose (rCMRglc) values obtained by betaP and autoradiography. In addition, the betaP-derived input function was similar to that obtained by manual sampling. Our findings show that reliable rCMRglc values can be obtained using betaP.