TSPO and Alzheimer disease: 2009). This was alleviated by the development of new and improved second/third‐generation TSPO ligands. Another limitation revealed by both pre‐clinical and clinical TSPO PET studies is that the small dynamic range of TSPO changes in AD. The amplitude of the change in TSPO expression observed in AD is moderate and often overlaps with what is observed in normal aging (Varrone and Nordberg 2015).