Mapping of change in cerebral glucose utilization using fluorine-18 fluorodeoxyglucose double injection and the constrained weighted-integration method

The authors developed a method for mapping the change in cerebral glucose utilization at two different physiological states using [¹⁸ F]fluorodeoxyglucose (FDC) double infection and the constrained weighted-integration method. The authors studied young normal subjects without (baseline-baseline group, n=5) and with (baseline-stimulation group, n=5) vibrotactile stimulation of the fingertips of the right hand. Dynamic scans were performed using positron emission tomography (PET) following an initial dose (the first session, 0-30 min) and an additional dose (the second session, 30-60 min). The parametric images of the net clearance of FDG from blood to brain (K*), unidirectional blood-to-brain clearance (K₁*), and cerebral metabolic rate of glucose (CMR_glc) of the two sessions were generated. The averaged subtraction (second minus first session) and t-statistic images were generated, which were rendered into Talairach´s stereotaxic coordinates and merged with the averaged magnetic resonance imaging (MRI) image. In the baseline-baseline group, regional K*, K₁* and CMR_glc in the first and second sessions were strongly correlated (r²=0.953, 0.935, and 0.951, respectively, n=330). In the baseline-stimulation group, significant increases in these estimates were obtained in the contralateral primary somatosensory cortex (SI) (from 3.43±0.78 to 4.02±1.01 ml/100 g/min for K*, 7.85±1.88 to 9.09±1.71 ml/100 g/min for K₁*, and 280±5.9 to 32.3±5.5 μmol/100 g/min for CMR_glc), while there were no significant changes in the ipsilateral SI (from 3.45±0.83 to 359±0.72 ml/100 g/min for K*, 8.17±2.33 to 837±1.75 ml/100 g/min for K₁ * and 29.5±8.1 to 29.1±8.2 μmol/100 g/mln for CMR _glc), Significant increases in K* and CMR_glc in the contralateral SI were clearly demonstrated in the t-statistic image. In conclusion, the proposed method allows mapping of changes in cerebral glucose utilization during physiological stimulation of the brain, and will be useful for studying the relationship between neural activity and regional cerebral glucose metabolism