Beta Amyloid PET Imaging for Alzheimer Disease With [18F]-Fluselenamyl

The investigators will first complete whole-body PET dosimetry studies in healthy adult normal volunteers to calculate the actual radiation dose of each human organ and determine the allowable dose for a human subject when receiving a single dose for a PET scan. Second, imaging of the brain and neck will be completed in a wide range of ages of healthy adult normal control participants and participants with mild cognitive impairment, both male and females to characterize 18F-Fluselenamyl uptake in the brain, its binding to beta-amyloid plaques, and radiolabeled metabolite will be completed. Amyloid is a protein related to dementia of Alzheimer's disease. 11C-PIB PET imaging and MRI of the brain will also be completed in the same participants and the data will be compared with 18F-Fluselenmayl. 11C-PIB and 18F-Fluselenamyl both bind to beta-amyloid plaques. Finally, a comparison of the normal control participants to patients with Alzheimer's disease will be completed.