Figure 1. Axial images of amyloid PET of two individuals with [11C]-PiB showing significant cortical uptake of the tracer (A - upper row - a “positive” scan, or A+) and absence of significant uptake of the tracer (B - lower row - a “negative” scan, or A-). In the A+ individual, a diffuse uptake is seen in the frontal, parietal, and temporal neocortices, as well as in the medial parietal and frontal lobes (precuneus, posterior and anterior cingulate gyrus), with an intensity similar to or more intense than the physiological uptake in the white matter. A negative scan (B) shows an uptake restricted to white matter tracts. Red localizers show the correct way to visualize the medial parietal and medial frontal cortices in the medial views (at the cortex level as localized in the coronal or axial views). Note the absence of uptake in the cerebellar cortex (a reference for negativity) and the physiological uptake in the brain stem (a reference for positivity).

Source: Images from the personal archive of one of the authors (A.M.C.) and acquired at the Nuclear Medicine Center of the Institute of Radiology, Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo (HCFMUSP), São Paulo, SP, Brazil.