1. From the Department of Radiology and Research Institute of Radiology (S.P., S.M.L., J.C., K.H.D., J.B.S.) and Department of Cardiothoracic Surgery (S.C.), University of Ulsan College of Medicine, Asan Medical Center, 88 Olympic-ro 43 Gil, Songpa-gu, Seoul 138-736, South Korea.