Authors: Konstantinos Chiotis Stephen F Carter Karim Farid Irina Savitcheva Agneta Nordberg for the Diagnostic Molecular Imaging DiMI network and the Alzheimer’s Disease Neuroimaging Initiative
Publish Date: 2015/07/02
Volume: 42, Issue: 10, Pages: 1492-1506
Abstract
Several radiotracers that bind to fibrillar amyloidbeta in the brain have been developed and used in various patient cohorts This study aimed to investigate the comparability of two amyloid positron emission tomography PET tracers as well as examine how age affects the discriminative properties of amyloid PET imagingFiftyone healthy controls HCs 72 patients with mild cognitive impairment MCI and 90 patients with Alzheimer’s disease AD from a European cohort were scanned with 11CPittsburgh compoundB PIB and compared with an age sex and disease severitymatched population of 51 HC 72 MCI and 84 AD patients from a North American cohort who were scanned with 18FFlorbetapir An additional North American population of 246 HC 342 MCI and 138 AD patients with a Florbetapir scan was split by age 55–75 vs 76–93 y into groups matched for gender and disease severity PET templatebased analyses were used to quantify regional tracer uptakeThe mean regional uptake patterns were similar and strong correlations were found between the two tracers across the regions of interest in HC ρ = 0671 p = 002 amyloidpositive MCI ρ = 0902 p 0001 and AD patients ρ = 0853 p 0001 The application of the Florbetapir cutoff point resulted in a higher proportion of amyloidpositive HC and a lower proportion of amyloidpositive AD patients in the older group 28 and 30 respectively than in the younger group 19 and 20 respectivelyThese results illustrate the comparability of Florbetapir and PIB in unrelated but matched patient populations The role of amyloid PET imaging becomes increasingly important with increasing age in the diagnostic assessment of clinically impaired patientsData used in preparation of this article were obtained from the Diagnostic Molecular Imaging DiMI network and the Alzheimer’s Disease Neuroimaging Initiative ADNI database adniloniuscedu As such the investigators within DiMI and ADNI contributed to the design and implementation of DiMI and ADNI and/or provided data but did not participate in analysis or writing of this report A complete listing of ADNI investigators can be found at http//adniloniuscedu/wpcontent/uploads/how to apply/ADNI Acknowledgement ListpdfAlzheimer’s disease AD pathology is characterised by the accumulation of amyloidbeta Aβ plaques neurofibrillary tangles and neuronal degeneration 1 2 The use of positron emission tomography PET with amyloidspecific radiotracers has enabled in vivo imaging of fibrillar Aβ plaques 11CPittsburgh compoundB PIB was the first generation of these tracers 3 The short halflife of 11C ~20 min led to the development of 18F derivatives halflife ~110 min 4 The longer halflife of 18F negates the need for onsite cyclotron and radiochemistry facilities as 18 F tracers can be produced centrally and delivered to geographically dispersed sites thus enabling their clinical use 18FFlorbetapir Florbetapir was the first 18 F radiotracer specific for Aβ to receive approval from both the US Food and Drug Administration FDA 2012 and the European Medicines Agency 2013 for assessing the presence of Aβ pathology in individuals with cognitive decline These advances in molecular imaging led to a proposed revision of the diagnostic criteria for AD in which amyloid PET plays an important role 5Autopsy studies of individuals who were scanned prior to death using PIB or Florbetapir have confirmed that both radiotracers bind selectively to fibrillar Aβ 6 7 8 9 Moreover in vivo studies have demonstrated the comparability of these two amyloid radiotracers within the same patient population 10 11 12 however it is uncertain how comparable PIB and Florbetapir are between different populations
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