1. From Stroke Service, Department of Neurology (H.A., L.H.S., K.L.F.) and AA Martinos Center for Biomedical Imaging, Department of Radiology (H.A., E.M.A., M.V., A.G.S.), Massachusetts General Hospital, Harvard Medical School, Boston, Mass; the Departments of Neurology and Epidemiology and Biostatistics (S.C.J.), University of California–San Francisco, San Francisco, Calif; and the National Institute of Neurological Disorders and Stroke (W.J.K.), National Institutes of Health, Bethesda, Md.