Selective PET Imaging of Astrocytes and Microglia in Alzheimer's Disease

Patients with Alzheimer's disease Inclusion criteria: * Individuals of either sex, 50-90 years of age. * Meeting research criteria for AD (McKhann, Knopman et al. 2011). * With a CDR (Morris 1993) score of 1-3. * Fluent in English or Spanish. * Have sufficient communication and comprehension ability to consent to the performance of the study or have a legally authorized representative. Exclusion criteria: * Inability to undergo MRI or PET for any reason, including severe claustrophobia. * History of large stroke or brain trauma, multiple sclerosis or other brain disorder that, in the judgment of the PI may confound the study. * Pregnancy. In women in whom the possibility of pregnancy cannot be excluded, a pregnancy test must be performed on site the morning of any PET visit and a negative result together with a physician interview are required prior to the administration or any radiopharmaceutical. * Research radiation exposure greater than 50 mSv effective dose within 12 months including radiation exposure from this study. Healthy volunteers: Inclusion criteria: * Individuals of 18-90 years of age. * Negative amyloid accumulation determined by PET (only for the comparison with AD). * Fluent in English. * Have enough communication and comprehension ability to consent to the performance of the study. Exclusion criteria: * Inability to undergo MRI or PET for any reason, including severe claustrophobia. * Brain disorder, other than idiopathic headache. * Current primary Axis I or II psychiatric disorder. * Current use of psychotropic or anti-epileptic medication. * Substance abuse during the past two years. * Active cancer, metabolic encephalopathy, infection, cardiovascular disease. * Active hematological, renal, pulmonary, endocrine or hepatic disorders, except for treated thyroid disease. * Pregnancy. In women in whom the possibility of pregnancy cannot be excluded, a pregnancy test must be performed on site the morning of any PET visit and a negative result together with a physician interview are required prior to the administration or any radiopharmaceutical * Research radiation exposure greater than 50 mSv effective dose within 12 months including radiation exposure from this study. * Only for the subjects undergoing the blocked scan with selegiline: known contraindications to selegiline, including hypersensitivity to the drug and use of opioids, such as meperidine and some antidepressants such as bupropion.