The high lipophilicity of [11C](R)PK11195 and its related limitations already mentioned led to the development of a second generation of TSPO tracers, which include but are not limited to the following: the phenoxyarylacetamide derivatives [11C]PBR28 and [18F]FEPPA; and pyrazolopyrimidines [11C]DPA-713, [123I]/[124I]/[125I]DPA-713, [18F]DPA-714 (PBR099) and [18F]F-DPA (Figure 1) [36]; most of these have been studied in humans, especially in mild cognitive impairment (MCI) and AD patients and in patients with Parkinson’s disease [6,10,11]. The gene discussed is TSPO; the disease is Alzheimer disease.