1. From the Division of Interventional Neuroradiology (G.R.D.), David Geffen School of Medicine at UCLA, Los Angeles, Calif; Concentric Medical, Inc. (G.W.), Mountain View, Calif; the Department of Neurosurgery (Z.-.S.S.), The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, P.R. China; and the Neurovascular Service, Department of Medicine (Y.L.), Madigan Army Medical Center, Tacoma, Wash.