Early-Phase¹⁸F-Florbetapir and¹⁸F-Flutemetamol Images as Proxies of Brain Metabolism in a Memory Clinic Setting

Abstract

Alzheimer disease (AD) neuropathologic changes are b-amyloid (Ab) deposition, pathologic tau, and neurodegeneration. Dual-phase amyloid PET might be able to evaluate Ab deposition and neurodegeneration with a single tracer injection. Early-phase amyloid PET scans provide a proxy for cerebral perfusion, which has shown good correlations with neural dysfunction measured through metabolic consumption, whereas the late frames depict amyloid distribution. Our study aimed to assess the comparability between early-phase amyloid PET scans and 18 F-FDG PET brain topography at the individual level and their ability to discriminate patients. Methods: One hundred sixty-six subjects evaluated at the Geneva Memory Center, ranging from no cognitive impairment to mild cognitive impairment and dementia, underwent early-phase amyloid PET-using either 18 F-florbetapir (eFBP) (n 5 94) or 18 F-flutemetamol (eFMM) (n 5 72)-and 18 F-FDG PET. Ab status was assessed. SUV ratios (SUVRs) were extracted to evaluate the correlation of eFBP/eFMM and their respective 18 F-FDG PET scans. The single-subject procedure was applied to investigate hypometabolism and hypoperfusion maps and their spatial overlap by the Dice coefficient. Receiver-operating-characteristic analyses were performed to compare the discriminative power of eFBP/eFMM and 18

Agreement between early-phase Amyloid-PET and pulsed Arterial Spin Labeling in a memory clinic cohort

“…For instance, a previous study observed different agreement between ePIB-PET and FDG-PET according to the amyloid status [24]. However, a recent study showed high agreement between ePET (using eFBP and eFMM tracers) and FDG-PET regardless of the amyloid positivity of the subjects [23]. Similarly, previous studies have shown an inverse relationship between amyloid deposition and CBF-ASL/FDG-PET [10].…”

“…Moreover, we acknowledge differences between the current ePET protocol and the previously used ones. Namely, we used eFBP and eFMM tracers and analysed the static images, which have been recently shown to be capable to detect perfusion with a similar e cacy than FDG-PET [23]. On the other hand, early PIB-PET uptake shows slightly lower association than the ratio of tracer in ux extracted from dynamic PIB-PET in comparison to FDG-PET [24], as well different spatial patterns between both techniques [10,25].…”

Clinical Effect of Early vs Late Amyloid Positron Emission Tomography in Memory Clinic Patients

“…Nevertheless, amyloid PET is less invasive and better accepted by patients (indeed, in arm 3, 11% of participants explicitly wanted to undergo an amyloid PET, and 5% underwent amyloid PET because they refused lumbar puncture), and it is the biomarker of choice when lumbar puncture is contraindicated. Moreover, recent evidence shows that a dual-phase acquisition of amyloid PET imaging can also offer information on cortical perfusion (a proxy of metabolism and thus a measure of neurodegeneration) when additional early-phase images are acquired after tracer injection …”

PET Imaging in Dementia: Mini-Review and Canadian Perspective for Clinical Use

“…9 This is mainly linked to the lack of studies showing, beyond its analytical and clinical validity, its impact on patients' management and care. With the first diseasemodifying therapies using amyloid-antibodies having been FDAapproved 55,56 , reimbursement status is gradually changing, as the proof of target expression may be required prior to initiation of an expensiveand not risk-freeantibody therapy. Currently, amyloid PET is reimbursed in Switzerland since August 2020, 84 in France since August 2022, 58 in the U.S since October 2023 59 and in Japan since November 2023.…”