PET Imaging of Phosphodiesterase-4 (PDE4) in Volunteers With Alzheimer Disease (AD) or Mild Cognitive Impairment (MCI)

Background: About 5 million adults in the United States have age-related brain disorders. These include Alzheimer disease (AD), mild cognitive impairment (MCI), and other dementias. The number of people with these disorders will likely increase as the population ages and life span increases. Inflammation is thought to play a role in AD and MCI. Researchers want to know if an enzyme called PDE4B increases inflammation in people with AD or MCI. Objective: To test whether medical imaging using a new radiotracer (\[18F\]PF-06445974) can measure PDE4B in the brains of people with AD or MCI. Eligibility: People aged 50 years and older with AD or MCI. Healthy volunteers are also needed. Design: Participants will have up to 5 clinic visits with 3 imaging scans of the brain. They will have be screened. They will have a physical exam with blood tests. This will include tests of their heart and nerve function, including memory. Participants will have 2 positron emission tomography (PET) scans. One will use a standard radiotracer. The other will use the study radiotracer. They will receive each tracer through a tube attached to a needle inserted into a vein. During the scan with the study tracer, participants will have a second tube inserted into a vein in the wrist; this tube will be used to draw blood during the scan. Participants will lie on a bed that slides into a doughnut-shaped machine. These visits will take about 6 hours each. Participants will have 1 magnetic resonance imaging (MRI) scan. They will lie on a bed that slides into a cylinder. This visit will take up to 2 hours....