Moreover, we do not want lack of communication to be a barrier to accrual. 5.3.2 PBR PET Scan Image Acquisition Details : During each visit, [11C]PBR28 (up to 15mCi, which results in ~3.7 mSv) will be injected intravenously with a slow bolus over a 30s period. The catheter will be flashed post-injection of with 0.9% saline solution. Dynamic data will be collected over approximately 90 minutes in list mode, and framed post- collection. At the beginning of the scan session, an intravenous catheter will be placed for tracer injection . A second line will be placed in the opposite arm from the injection site and will be used to draw 2mL or 12mL blood samples throughout the test, for at mos t 200m L of blood. The blood draws will be used to assess the radioactivity levels in the blood necessary for dynamic imaging. The catheter s will be removed at the end of the study. Image Analysis Details : PET volumes will be reconstructed using the ordinary Poisson ordered subsets expectation maximization (OP -OSEM) 3D algorithm. Corrections will be applied for variable detector dead time and efficiency, random coincidences, photon attenuation and scatter, and decay.