title: Validation of true low-dose18F-FDG PET of the brain.
abstract: The dosage of18F-FDG must be sufficient to ensure adequate PET image quality. For younger patients and research controls, the lowest possible radiation dose should be used. The purpose of this study was to find a protocol for FDG-PET of the brain with reduced radiation dose and preserved quantitative characteristics. Eight patients with neurodegenerative disorders and nine controls (n=17) underwent FDG-PET/CT twice on separate occasions, first with normal-dose (3 MBq/kg), and second with low-dose (0.75 MBq/kg, 25% of the original). Five additional controls (total n=22) underwent FDG-PET twice, using normal-dose and ultra-low-dose (0.3 MBq/kg, 10% of original). All subjects underwent MRI. Ten-minute summation images were spatially normalized and intensity normalized. Regional standard uptake value ratios (SUV-r) were calculated using an automated atlas. SUV-r values from the normal- and low-dose images were compared pairwise. No clinically significant bias was found in any of the three groups. The mean absolute difference in regional SUV-r values was 0.015 (1.32%) in controls and 0.019 (1.67%) in patients. The ultra-low-dose protocol produced a slightly higher mean difference of 0.023 (2.10%). The main conclusion is that 0.75 MBq/kg (56 MBq for a 75-kg subject) is a sufficient FDG dose for evaluating regional SUV-ratios in brain PET scans in adults with or without neurodegenerative disease, resulting in a reduction of total PET/CT effective dose from 4.54 to 1.15 mSv. The ultra-low-dose (0.5 mSv) could be useful in research studies requiring serial PET in healthy controls or children.
authors.affiliation: Department of Surgical Sciences, Radiology, Uppsala University Uppsala, Sweden.
authors.forename: David
authors.initials: D
authors.lastname: Fällmar
authors.affiliation: Department of Surgical Sciences, Nuclear Medicine and PET, Uppsala UniversityUppsala, Sweden; Hermes Medical SolutionsStockholm, Sweden.
authors.forename: Johan
authors.initials: J
authors.lastname: Lilja
authors.affiliation: Department of Public Health and Caring Sciences, Geriatrics, Uppsala University Uppsala, Sweden.
authors.forename: Lena
authors.initials: L
authors.lastname: Kilander
authors.affiliation: Department of Surgical Sciences, Nuclear Medicine and PET, Uppsala University Uppsala, Sweden.
authors.forename: Torsten
authors.initials: T
authors.lastname: Danfors
authors.affiliation: Department of Surgical Sciences, Nuclear Medicine and PET, Uppsala University Uppsala, Sweden.
authors.forename: Mark
authors.initials: M
authors.lastname: Lubberink
authors.affiliation: Department of Surgical Sciences, Radiology, Uppsala University Uppsala, Sweden.
authors.forename: Elna-Marie
authors.initials: EM
authors.lastname: Larsson
authors.affiliation: Department of Surgical Sciences, Nuclear Medicine and PET, Uppsala University Uppsala, Sweden.
authors.forename: Jens
authors.initials: J
authors.lastname: Sörensen
keywords: FDG; PET; methodology; neurodegeneration; neuroimaging