TSPO and Alzheimer disease: In vivo, microglial activation can be detected using positron emission tomography (PET) ligands for the TSPO,11–13 and the reversible antagonist at TSPO [11C]-(R)-PK11195 is often used for studying diseases that involve microglial activation or the recruitment of macrophages as in multiple sclerosis,14 stroke,15,16 Alzheimer disease,17 traumatic brain injury,18 and to monitor brain lesions.19