Figure 3a.

(a) Axial ¹⁸F florbetapir PET images obtained in a healthy patient demonstrate nonspecific cerebellar and cerebral white matter uptake (arrows) with minimal gray matter activity. (b) Axial ¹⁸F florbetapir PET images obtained in a patient with known Alzheimer disease demonstrate normal white matter uptake (arrow) and minimal gray matter uptake in the cerebellum, but marked cerebral gray matter uptake that makes gray matter–white matter differentiation difficult.