1. From the Cardiovascular Imaging Center, Cardiovascular Division, Department of Internal Medicine (S.-J.R., H.L.-P., J.R.L., S.K.), the Department of Neurosurgery (D.C., D.E., N.F.K.), and the Division of Neurosurgical Anesthesia, Department of Anesthesia (H.M., M.D.), University of Virginia, Charlottesville.