Positron Emission Tomography (PET) to Study Brain Signaling

This study uses positron emission tomography (PET) to examine brain function and signaling involving phospholipids, and to see how signaling is related to blood flow. Much of the brain is composed of fatty molecules called phospholipids. These molecules are involved in the way brain cells signal each other to direct brain function. Brain disease may change phospholipids and disturb brain structure and signaling. Studies of brain phospholipid composition and metabolism may help clarify how the brain works in healthy people or stops working effectively in disease states. Healthy volunteers between 18 and 45 years of age may be eligible for this study. Candidates are screened with a medical history, physical examination, and blood and urine tests. Participants undergo magnetic resonance imaging (MRI) and PET scanning as follows: MRI MRI uses a magnetic field and radio waves to produce images of body tissues and organs. For this procedure, the subject lies on a table that is moved into a metal cylinder (the scanner) and wears earplugs to muffle loud knocking and thumping sounds that occur during the scanning process. Scanning time varies from 20 minutes to 3 hours, with most scans lasting between 45 and 90 minutes. Subjects may be asked to lie still for up to 30 minutes at a time. PET For the PET scan, a catheter (thin plastic tube) is inserted into an artery in the subject's wrist or elbow crease to collect blood samples during the procedure, and a second catheter is placed in a vein in the opposite arm to inject radioactive tracers. The subject lies on the scanner bed, wearing a special facemask and goggles. The mask helps hold the head still during the scans, and the goggles either block all light or administer bright flashing lights. Radioactive water is injected into the vein, followed by a 1-minute PET scan to measure brain blood flow. This is repeated three more times. Then, a radioactive fatty acid is injected into the vein, followed by a 1-hour PET scan to