Characterisation of Posterior Predominant Amyloid PET Binding Across Multiple Cohorts.

The standard approach to quantify amyloid (Aβ) PET averages uptake within a single cortical mask that assumes no clinically relevant spatial heterogeneity in uptake patterns. Here, in a sample of 12,379 clinically impaired participants taken from four phenotypically diverse cohorts we use data-driven approaches to discover heterogeneous patterns of Aβ-PET binding, uncovering a reproducible and clinically relevant pattern of posterior predominant Aβ-PET binding. In particular, Aβ-PET positive participants who have posterior predominant binding are less likely to be APOE-ε4 carriers, more severely impaired, have thinner cortex in posterior regions, and greater posterior tau PET burden. Furthermore, in a subsample of participants with neuropathological assessment, participants with posterior predominant Aβ binding have a higher likelihood of having cerebral amyloid angiopathy at autopsy. These findings suggest that Aβ-PET accumulates along two orthogonal axes with biological and clinical relevance, indicating that the standard approach to assess Aβ-PET is insufficient to capture meaningful signal from Aβ-PET imaging. This work has implications for the diagnosis and treatment of Alzheimer's disease and extends our understanding of the mechanisms governing variable Aβ-PET distribution and its downstream effects.