1. From the Department of Radiology and Research Institute of Radiology (J.E.P., H.S.K., S.C.J.), Department of Clinical Epidemiology and Biostatistics (S.Y.P.), and Department of Neurosurgery (J.H.K.), University of Ulsan College of Medicine, Asan Medical Center, 43 Olympic-ro 88, Songpa-Gu, Seoul 05505, Korea; and Department of Radiology, Johns Hopkins University, Baltimore, Md (H.Y.H.).