1. From the Departments of Medical Imaging (J.C., J.F., A.P.C., J.P., D.M.M., D.J.M.), Neurology (F.L.S.), and Neurosurgery (J.F., M.T.), Toronto Western Hospital, Toronto, Ontario, Canada; the Departments of Medical Imaging (D.J.M.) and Physiology (J.S.H., M.T., J.A.F.), University of Toronto, Toronto, Ontario, Canada; and the Department of Anesthesia (J.S.H., J.A.F.), Toronto General Hospital, Toronto, Ontario, Canada.