The use of an individual-based FDG-PET volume of interest approach in mild cognitive impairment: a multi-modality longitudinal follow-up study

Abstract

Abstract Background: Based on a longitudinal cohort design, the aim of this study was to investigate whether individual-based 18F fluorodeoxyglucose positron emission tomography (18F-FDG-PET) regional signals can predict dementia conversion in patients with mild cognitive impairment (MCI). Methods: We included 44 MCI converters (MCI-C), 38 non-converters (MCI-NC), 42 patients with amyloid-positive Alzheimer disease, and 40 cognitively normal controls. Data from annual cognitive measurements, 3D T1 magnetic resonance imaging (MRI) scans, and 18F-FDG-PET scans were used for outcome analysis. An individual-based FDG-PET approach was defined using seven volumes of interest (VOIs), Z transformed using a normal FDG-PET template. Hypometabolism was defined as a Z score < -2 of regional standard uptake value ratio. For the longitudinal cognitive test scores, generalized estimating equations were used. A linear mixed effect model was used to compare the time effect of cortical hypometabolism and cortical thickness degeneration. Results The clinical follow-up period was 6.6 ± 3.8 years (range 3.1 to 16.0 years). The cognitive decline trends could differentiate MCI-C from MCI-NC after 3 years of follow-up. In MCI at the first 18F-FDG-PET scan, medial temporal lobe (94.7% sensitivity, 80.5% specificity) and posterior cingulate cortex (89.5% sensitivity, 73.1% specificity) hypometabolism predicted conversion with high accuracy. 18F-FDG-PET hypometabolism preceded dementia conversion at an interval of 3.70 ± 1.68 years and was earlier than volumetric changes. Conclusions Our analysis support the use of individual-based 18F-FDG-PET analysis to predict MCI conversion. Changes in 18F-FDG-PET occurred 1 to 8 years prior to dementia conversion, and hypometabolism occurred 2 years before MRI findings.