MAPT and Alzheimer disease: Since then, four families of tracers in particular have shown promise in the assessment of AD and MCI: [11C]PBB3, from the same tracer family as [11C]PiB, the THK aryquinoline derivatives, the pyrido‐indole derivative [18F]AV‐1451, and recently developed second‐generation tau tracers (Table 3).