Fleisher AS, Chen K, Roontiva A, Thiyyagura P, Liu X, Clark CM, Mintun MA, Pontecorvo MJ, Doraiswamy PM, Reiman EM.
Multi-level fibrillar amyloid thresholds of florbetapir F18 PET images from five multi-center studies.
Human Amyloid Imaging 2011 Meeting Abstracts. 2011 Jan 15;
Objectives: To characterize quantitative and visual florbetapir F18 positron emission tomography (PET)
measurements of fibrillar amyloid-s (As) burden in a large clinical cohort of probable Alzheimer's disease (pAD),
mild cognitive impairment (MCI), and older healthy controls (oHC); and to assess percent positivity of those meeting
empirically predetermined florbetapir PET criteria associated with an intermediate-to-high likelihood of pathologic
AD (pathAD) or having gany Ash pathology above that typically seen in young-low-risk individuals.
Methods: PET scans and clinical evaluations were analyzed for 210 participants from 5 multicenter
studies. Cerebral-to-whole-cerebellar florbetapir standard-uptake-value ratios (SUVRs) were computed in
68 pAD, 60 MCI, and 82 oHCs (.55 years old). A threshold of SUVRs .1.17 was used to reflect pathAD based on
separate antemortem PET and postmortem neuropathology data from 19 end-of-life patients; Similarly a threshold
of SUVRs >1.08 was used to signify gany Ash as this was the upper limit from a separate set of 46 18-40 year-old
Results: The pAD, MCI, and oHC participants differed significantly in mean cortical florbetapir SUVRs
(1.39}0.24>1.17}0.27>1.05}0.16; p 40.0>20.7%, p 46.6>28.1%,
p 1.03}0.16, p = 0.048).
Conclusions: This analysis supports the ability of florbetapir PET SUVRs to characterize As levels in clinical pAD,
MCI, and oHC groups, and in oHC APOE4 carriers and noncarriers, using continuous and dichotomous measures
of fibrillar As burden. It introduces criteria to determine whether an image is associated with As of intermediateto-
high likelihood of pathologic AD or with gany Ash levels.