1. From the Department of Radiology (J.M.R., H.K., J.H., R.G.G.), Department of Emergency Medicine (J.G.), and Department of Neurology (H.B.B., J.R.), Massachusetts General Hospital, Harvard University, Boston, MA; Department of Radiology, Peking Union Medical College Hospital, Beijing, China (J.L.); and Department of Interventional Neuroradiology, Neuroscience Institute, Abbott Northwestern Hospital, Minneapolis, MN (J.D.-A.).