\[18F\]Florbetazine (\[18F\]92) is a molecularly targeted imaging agent for Aβ protein with a novel diaryl-azine scaffold. It has shown specific binding affinity to Aβ aggregates in postmortem human AD brains and excellent brain pharmacokinetic properties with little non-specific retention in white matter in animal studies and a limited number of patients with Alzheimer's Disease (AD). The purpose of the current study is to examine the binding properties of \[18F\]Florbetazine in human subjects and to compare the cortical and white matter binding with \[11C\]PiB or \[18F\]Florbetapir in the same subjects. Imaging of the brain will be completed in healthy adult normal control participants and participants with cognitive impairment (including probable AD and dementia due to other conditions) to characterize \[18F\]Florbetazine uptake in the brain and its binding properties. \[11C\]PIB or \[18F\]Florbetapir PET imaging along with MRI will be completed in the same participants and the data will be compared with 18F-\[18F\]Florbetazine.