Biodistribution of [11C]PIB in Patients With Risk Factors for Alzheimer's Disease

Brain amyloid will be measured using PET with \[11C\]PiB. Participation will involve an initial brain scan and possibly a follow-up brain scan two years later. The data collected in this study will help explain amyloid deposits in several groups of participants including adults with and without signs of memory impairment. The information collected will help find out who is more likely to have brain amyloid and when it increases the risk for developing memory problems. Research studies suggest that people with elevated levels of brain amyloid are at an increased risk for memory decline, but this does not mean that every person with amyloid build up will develop AD.