PET Imaging Study Using [11C]PIB in Subjects With AD & Healthy Volunteers

The objectives of the study are: 1. To perform PET scans with \[11C\]PIB to use for direct (i.e., same-subjects) comparison of \[11C\]PIB and \[18F\]AV-45 2. To establish the most effective and reliable PET imaging method to detect amyloid deposition in AD, in order to understand disease progression and subsequently evaluate treatment effects. 3. To ascertain a PET imaging method that will minimize discomfort for subjects, thus increasing the potential for clinical follow-up scans, by reducing the patient burden and potential cost of future PET examinations. A separate protocol/study will be conducted using \[18F\] AV-45. Participants who enroll in this protocol using \[11C\] PIB will be consented to participate in the \[18F\] AV-45 (IRB # NA\_00033155) protocol/study as it is a mandatory requirement that participants participate in both protocols.Up to 20 participants with mild to moderate Alzheimer's Disease and 10 healthy volunteers will participate in this study.