From the Department of Neuroradiology (R.G.N., R.F., P.E.G., R.G.G.), Massachusetts General Hospital, Harvard Medical School, Boston, MA; Departments of Neurology, Neurosurgery, and Radiology (R.G.N.), Emory University School of Medicine, Marcus Stroke and Neuroscience Center, Grady Memorial Hospital, Atlanta, GA; Department of Radiology (S.E.M.), Brigham and Women's Hospital, Harvard Medical School, Boston, MA; National Institutes of Health (W.J.K.), Washington, DC; Department of Neurology,... (At 2012-02)