TSPO and Alzheimer disease: Nevertheless, some studies using second generation TSPO tracers with generally better signal to noise ratios ([18F]DPA-714, [11C]PBR28, [18F]FEDAA1106 & [18F]FEPPA) could also not find significant differences in TSPO PET signal between AD and controls [25–28], while others found higher TSPO PET binding in AD compared to controls [4, 5, 22, 24].