FDG Uptake of Normal Canine Brain Assessed by High-Resolution Research Tomography-Positron Emission Tomography and 7 T-Magnetic Resonance Imaging

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The purpose of this study was to assess the normal distribution of ¹⁸F-fluoro-2-deoxy-D-glucose (FDG) uptake of canine brain structures using a high-resolution research tomography-positron emission tomography (HRRT-PET) and 7 T-magnetic resonance imaging (MRI) fusion system. FDG-PET and T2-weighted MRI of the brain were performed on 4 healthy laboratory beagle dogs. On MRI, regions of interests (ROIs) were manually drawn over 51 intracranial structures, including nine gross structures and 42 detailed structures. Relative standard uptake value ratio (rSUV=SUV of ROI/SUV of whole brain) was calculated for each ROI. The HRRT-PET and 7 T-MRI fusion imaging system demonstrated significant differences in glucose metabolism among various intracranial structures. Among gross structures, the midbrain and the pons and medulla oblongata had the highest uptake (rSUV: 1.12 ± 0.03) and lowest uptake (rSUV: 0.90 ± 0.06) of FDG, respectively. When rSUVs were calculated on detailed regions, the caudal colliculus and the longitudinal fibers of pons had the highest (rSUV: 1.62 ± 0.05) and the lowest (rSUV: 0.63 ± 0.03) glucose metabolism, respectively. Because the high resolution of PET-MRI fusion images provided clearly identifiable metabolic activities of canine brain, the HRRT-PET and 7 T-MRI fusion imaging might be a good tool for evaluation of intracranial diseases in canines.