Background: A comparison of the distribution of PiB accumulation as seen on PET with the distribution of amyloid
pathology seen on autopsy is of great interest in understanding PiB binding in vivo. Very limited autopsy/PiB
correlative data exists in the literature. In this report we describe the findings of PiB scans as compared to autopsy
findings on 5 subjects.
Methods: Five subjects (4 male, 1 female) who underwent antemortem PiB PET scans subsequently came to
autopsy. Diagnoses were of AD (CDR global = 2), naMCI (CDR global = 1.0), aMCI (CDR global = 0.5), LBD (CDR
global = 0.5), and normal control (CDR global = 0.0). They expired 9, 17, 16, 32 and 24 months after their PiB
scans, respectively. The quantitative distribution of PiB on PET imaging was compared in the frontal (Fr), parietal
(Par), temporal (Tem), occipital (Occ) and hippocampal (Hip) regions to the distribution of diffuse plaques, cored
plaques and vascular amyloid, evaluated with beta-amyloid immunohistochemistry (Novacastra, NCL-B-amyloid;
clone 6F/3D) at autopsy.
Results: PiB scans showed increased PiB binding in the subjects with AD, aMCI and LBD (global PiB cerebellar
ratios = 2.7, 1.7 and 1.5) but not in the naMCI or control subjects (global PiB cerebellar ratios = 1.3 and 1.4). At
autopsy, the AD, aMCI and LBD subjects showed frequent numbers of diffuse and cored amyloid plaques in
neocortical areas and variable amyloid angiopathty. In the naMCI and control subjects there was a conspicuous
absence of amyloid deposits (diffuse and compact plaques) and amyloid angiopathy in all areas sampled.
Conclusions: These results are consistent with the expected finding that PiB accumulation occurs in subjects
with AD, aMCI, and LBD although with some variability and reflects the frequency of microscopic amyloid deposits
at autopsy. The findings are also consistent with the idea that subjects with naMCI are less likely to have AD-like
pathological substrate, and more likely to have prodromal, non-AD dementia.
Grant support: National Institute on Aging [P50 AG16574, U01 AG06786, K23 AG030935 and R01 AG11378];
the Robert H and Clarice Smith and Abigail Van Buren Alzheimer's Disease Research Program; and the Alexander
Family Alzheimer’s Disease Research Professorship of the Mayo Foundation, USA.
