1. Department of Radiology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
2. Department of Radiology, Research Institute of Radiological Science, Yonsei University College of Medicine, Severance Hospital, Seoul, Korea.
3. Department of Radiology and Research Institute of Radiology, Asan Medical Center, Seoul, Korea.
4. Department of Radiology, Seoul National University Hospital, Seoul, Korea.