Metabolic functional connectivity.

1796 Objectives Functional magnetic resonance imaging (fMRI) is used to map functional connectivity (FC) between brain regions on the basis of synchronous oscillations of blood-oxygen-dependent (BOLD) signals. FC is sensitive to genetic variability, brain states, development, gender, aging, and disease. PET imaging with FDG has been extensively used as a static marker of brain function (metabolic images average activity over 15-30 minutes) but recent findings indicate that it is also sensitive to dynamic changes in brain activity. Here we assess whether we can use dynamic FDG imaging to map metabolic functional connectivity (MFC) at rest. Methods Twenty eight healthy volunteers (36 ± 12 years; 11 females) were scanned with PET (HRRT; ~2.5 mm resolution) and FDG (10 mCi) using list-mode acquisition initiated after FDG injection for a total of 75 min while resting in the scanner (eyes open). The resulting dynamic FDG (dFDG) images with 10 seconds temporal resolution (total 450 time frames) were resampled to 3mm isotropic resolution. The dFDG data was aligned to the subject’s structural MRI image, which was normalized to the MNI template. Band-pass filtering was performed in order to remove slow trends in dFDG data (0.001-0.05 Hz). Seed-voxel correlations and Functional Connectivity Density (FCD) mapping were used to map MFC and assess the strength of connectivity hubs. SPM8 was used for statistical analyses. Statistical significance was defined using a cluster-level corrected PFWE Results Consistent with previous findings obtained with fMRI for FC, here we show that regions with strongest connectivity were located in visual cortex and precuneus. However, in contrast to prior FCD findings, MFC additionally revealed that the prefrontal cortex and cerebellum were regions with strong MFC. Conclusions Our results indicate that dFDG can be used to map metabolic connectivity between brain regions on the basis of coordinated slow oscillations on metabolic activity. Future studies should investigate the relationship between FC and MFC.