1. Department of Radiology, Chonbuk National University Medical School and Hospital, Research Institute of Clinical Medicine, Jeonju 561-712, Korea.
2. Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Seoul 138-736, Korea.
3. Department of Radiology, Hallym University College of Medicine, Hallym University Sacred Heart Hospital, Anyang 431-796, Korea.
4. Department of Radiology, Seoul Medical Center, Seoul 131-865, Korea.