Fig. 1.
Baseline and longitudinal PET data support a classification in three sequential stages according to cortical and striatal signals. Top row: PET data in the striatum versus cortex from the HABS (C11PiB) and the ADNI (F18Florbetapir). Striatum can distinguish two groups among individuals with high cortical Aβ. Subjects with PET-Aβ stage 1 have striatal signal in the same range compared with low-Aβ CN participants, and subjects with PET-Aβ stage 2 participants have striatal signal above the 99th percentile of low-Aβ normal participants. Bottom row: Spaghetti plots showing longitudinal change in striatal and cortical Aβ PET in both cohorts over a 3-year follow-up (Table 2 and text for statistics). Plain arrows indicate the most frequent transition observed. The dotted red arrow highlights the backward transitions observed in ADNI only. Abbreviations: Aβ, amyloid β; ADNI, Alzheimer’s Disease Neuroimaging Initiative; CN, clinically normal; HABS, Harvard Aging Brain study.