In frontal, posterior cingulate, parahippocampal, lateral and posterior temporal cortex, precuneus, and hippocampus, increased TSPO binding was found in MCI patients compared to controls. In a mixed group of 16 MCI and AD patients with high Aβ, microglial activation was correlated with PiB amyloid uptake in frontal, parietal, and lateral temporal areas. Here, TSPO is linked to Alzheimer disease.