TSPO and Alzheimer disease: Although to limit participant radiation exposure, we did not compare head-to-head two TSPO PET tracers, as we have done in previous studies,33,67 regions with significantly increased 11C-ER176 signal compared favourably with those reported in AD using other recent tracers.68,69,70,71 As with other TSPO tracers, including 11-C-PK11195,26 binding was influenced by the TSPO polymorphism.