Analysis of 18F-XTR006 PET Imaging in Cognitively Normal Subjects, and Patients With MCI and AD

This study is evaluating a new experimental PET scan tracer called 18F-XTR006 to see how well it can detect tau protein buildup in the brain — a key feature of Alzheimer's disease. It will be tested in cognitively normal adults, those with early memory problems (MCI), and those with Alzheimer's disease. **You may be eligible if...** - You are 50 or older - You can tolerate both PET and MRI scans - You fall into one of three groups: cognitively normal (CDR score 0, normal memory test), mild cognitive impairment (MCI), or Alzheimer's disease — with supporting brain scan evidence **You may NOT be eligible if...** - You have another type of dementia (such as Lewy body or frontotemporal) - You have significant psychiatric illness preventing you from completing scans - You have large strokes or brain tumors shown on MRI - You have claustrophobia or a history of alcohol or drug dependence - You are pregnant or breastfeeding Talk to your doctor to see if this trial is right for you.