Concordance of early-phase amyloid PET and FDG PET across the Alzheimer spectrum
Poster No:
1997
Submission Type:
Abstract Submission
Authors:
William Aye1, Campbell Le Heron1, Ross Keenan2, Lynette Tippett3, Tim Anderson1, Tracy Melzer4
Institutions:
1University of Otago, Christchurch, Canterbury, New Zealand, 2Pacific Radiology Canterbury, Christchurch, Canterbury, New Zealand, 3University of Auckland, Auckland, New Zealand, 4University of Canterbury, Christchurch, Canterbury, New Zealand
First Author:
Co-Author(s):
Introduction:
18F-Fluorodeoxyglucose (FDG) positron emission tomography (PET), amyloid PET, and arterial spin labelling (ASL) MRI are currently used to image cerebral metabolism, amyloid accumulation, and perfusion in Alzheimer's disease and other conditions. Emerging evidence indicates that images acquired immediately after amyloid tracer injection ('early-phase') may offer a surrogate measure of metabolism and/or perfusion (Boccalini et. al., 2022). A 'dual-phase' PET approach may therefore have the potential to provide information about both metabolism/perfusion and pathological protein accumulation from a single radiotracer injection. Here, we evaluated the relationship among FDG PET, dual-phase 18F-Florbetaben (FBB) amyloid PET, and ASL MRI in a cohort of individuals assessed for cognitive impairment.
Methods:
Twenty participants were recruited from volunteers at the Dementia Prevention Research Clinic (Tippett et. al., 2022) and through private neurologist clinic referrals at the New Zealand Brain Research Institute, Christchurch, New Zealand. Participants completed the Addenbrooke's Cognitive Examination (ACE) and three scanning sessions: dual-phase FBB, FDG, and 3T ASL MRI. After injection of 308±40MBq FBB, early-phase images were acquired from 0 to 5 minutes, and late-phase images from 90 to 110 minutes post-injection using GE's SharpIR reconstruction algorithm. A low-dose CT scan was acquired immediately prior to PET acquisition for attenuation correction. On a separate day, FDG PET (215±23MBq) was acquired from 30-45 post-injection. The MRI protocol included a 3D T1-weighted and a 3D pseudo-continuous ASL prototype sequence. All three PET images (early-phase FBB (eFBB), late-phase FBB, and FDG) were coregistered to the T1 MRI and normalized to MNI space (using SHOOT in CAT12). SUVR images were calculated by scaling to the mean signal in the Centiloid project whole cerebellum, and smoothed (8mm). Mean values of eFBB, FDG, and ASL perfusion were extracted from regions within the AAL3 atlas. We investigated associations among eFBB, FDG, and ASL perfusion (1) within-subject, (2) across regions, and (3) voxel-wise.
Results:
eFBB and FDG exhibited significant associations both within-subject (within-subject median r [range] = 0.86 [0.69–0.95], p<0.001), and across regions of the AAL3 atlas (median r [range] = 0.81 [0.62–0.95], p<0.001). Additionally, eFBB and FDG PET showed significant voxel-wise associations in widespread cortical and subcortical grey matter regions (Figure 1, FWE-corrected p<0.05). ASL perfusion exhibited weaker correlations with both eFBB (median r = 0.36) and FDG (median r = 0.4) across regions.
Conclusions:
Early-phase FBB PET showed strong within-subject and regional correlations with FDG PET, but less with ASL perfusion. Dual-phase amyloid PET imaging provides a unique opportunity to assess pathological protein and underlying metabolism within a single scanning session. While the current work is restricted to a relatively small cohort and needs external validation, this technique may reduce costs, radiation exposure, and physical burden for patients, and streamline diagnosis, patient selection, and progress monitoring, especially in the context of emerging therapeutics for Alzheimer's disease.
Novel Imaging Acquisition Methods:
PET 1
Physiology, Metabolism and Neurotransmission:
Cerebral Metabolism and Hemodynamics 2
Keywords:
Positron Emission Tomography (PET)
Other - Metabolism
1|2Indicates the priority used for review
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Tippett, L. J. et. al. (2022). Dementia Prevention Research Clinic: a longitudinal study investigating factors influencing the development of Alzheimer’s disease in Aotearoa, New Zealand. Journal of the Royal Society of New Zealand, 53(4), 489–510.