1 Department of Radiology and Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Republic of Korea. dokh@amc.seoul.kr.
2 Department of Radiology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Republic of Korea.
3 Department of Radiology, Seoul National University College of Medicine, Seoul, Republic of Korea.
4 Department of Radiology, Seoul National University Hospital, Seoul, Republic of Korea.