Individually Differentiated Serotonergic Raphe Nuclei Measured with Brain PET/MR Imaging

Abstract

To measure the activity of individual raphe nuclei with fluorine 18 fluorodeoxyglucose (FDG) and carbon 11 ((11)C) 3-amino-4-(2-dimethylaminomethylphenylthio) benzonitrile (DASB) imaging using a brain positron emission tomography(PET)/magnetic resonance (MR) imaging fusion system. The study was approved by the Institutional Review Board of Gil Medical Center, and all volunteers provided written informed consent. FDG PET, (11)C-DASB PET, and T2*-weighted MR images from seven healthy volunteers were acquired by using a PET/MR imaging fusion system. The standard uptake value ratio (SUVR) of FDG (FDG-SUVR) and nondisplaceable binding potential (BPnd) of (11)C-DASB (DASB-BPnd) were determined for each raphe nucleus. A Pearson correlation analysis was performed to show the correlation between FDG-SUVR and DASB-BPnd for the raphe nuclei. Each raphe nucleus could be distinguished in both FDG (identifiability ratio, 0.86; κ = 0.77) and (11)C-DASB (identifiability ratio, 0.89; κ = 0.72) images. The mean values of DASB-BPnd for each raphe nucleus from dorsal to caudal direction were 6.08 (raphe nucleus 1), 5.93 (raphe nucleus 2), 3.86 (raphe nucleus 3), 3.18 (raphe nucleus 4), and 2.74 (raphe nucleus 5); the mean FDG-SUVR values were 1.00 (raphe nucleus 1), 1.00 (raphe nucleus 2), 0.87 (raphe nucleus 3), 0.94 (raphe nucleus 4), and 0.90 (raphe nucleus 5). FDG-SUVR and DASB-BPnd for the raphe nuclei were significantly correlated (r = 0.506, P = .002). Serotonergic activity, both glucose metabolism and transporter binding potential of raphe nuclei, were measured with a brain-dedicated PET/MR imaging system and showed a significant correlation.