Abstract
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Objectives Amyloid-beta (Aβ) imaging with 11C-PIB shows a robust increase in cortical binding in Alzheimer's disease (AD). The aim of this study is to explore the clinical potential of 11C-PIB imaging for the detection of amyloid burden at a very early preclinical stage in high risk subjects and compare it to 18F-FDG metabolism.
Methods 100 cognitively normal participants from Wisconsin Registry for Alzheimer’s Prevention (WRAP) (age, 60 +/- 5.9y) underwent 11C-PIB PET, 18F-FDG PET, and comprehensive neuropsychological testing. 11C-PIB distribution volume ratio (DVR) images were computed utilizing a cerebellar reference. Both the PIB DVR and FDG SUVR images were visually rated separately by 2 readers as 0 (normal), 1 (possible AD pattern), or 2 (probable AD pattern).
Results No subject received an FDG score of 2. 3.5% subjects had FDG score of 1 and 15% subjects had a PIB score of 1 or 2. 6/7 (86%) FDG score of 1participants showed PIB reading of 1 or 2. Association between PIB and FDG was significant for both readers. Inter-reader agreement is higher for PIB than it is for FDG. Compared to PIB- participants, PIB+ participants were more likely to be APOE4 positive (50% vs. 29%).
Conclusions We found evidence for Aβ aggregation in 15% of cognitively-normal late-middle age adults and this was significantly influenced by APOE. Visual analysis of PIB images is more consistent between readers than FDG for identification of AD pattern. Furthermore, amyloid burden seems to occur earlier than abnormal metabolism in high risk subjects for AD.
Research Support Alzheimer's Association NIRGD, NIA 5R01AG021155-0
Visual reading results of PIB and FDG images for 100 cognitively normal late middle-aged adults
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