A Phase II Trial of 18F-AV-45 Positron Emission Tomography (PET) Imaging in Healthy Volunteers, Patients With Mild Cognitive Impairment (MCI) and Patients With Alzheimer's Disease (AD)

Inclusion Criteria AD: * Male or female \>=50 years of age * Meet National Institute of Neurological and Communicative Diseases and Stroke/Alzheimer's Disease and Related Disorders Association (NINCDS) criteria for probable AD with MMSE score of 10-24 Inclusion Criteria MCI: * Male or female \>=50 years of age * Have a Clinical Dementia Rating (CDR) of 0.5 * MMSE \>24 Normal subjects: * Male or female \>=50 years of age * MMSE \>=29 * Normal on psychometric test battery at screening * Provide informed consent Exclusion Criteria: * Have a history or current diagnosis of other neurologic disease * Have had or currently have a diagnosis of other neurodegenerative disease * Have participated in experimental therapy targeted to amyloid plaque