TSPO and Alzheimer disease: Using [11C](R)-PK11195, [11C]-PBR28, or some other TSPO-specific radiotracers, AD patients all showed significantly increased regional TSPO ligand binding in the cortices compared to controls.134–136 In addition, microglial activation was found in the white matter.137 Microglial activation has also been detected by PET in patients with mild cognitive impairment (MCI).138–140 In MCI, microglial activation was positively correlated with amyloid load.141,142