TSPO and Alzheimer disease: Since increased TSPO expression in activated microglia has been associated with a number of neurological diseases (reviewed in Venneti et al., 2006), several PET tracers for TSPO (e.g.,; [11C](R)-PK11195, [11C]PBR28, [11C]DAA1106, [11C]AC5216, and [18F]DPA-714) have been studied to visualize the microglial activation in animal models and AD patients (Jacobs et al., 2012; Mori et al., 2012; Golla et al., 2015).