1. Department of Radiology, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul 110-746, Korea.
2. Department of Radiology, Kangwon National University College of Medicine, Chuncheon 200-722, Korea.
3. Department of Radiology, Korea University Guro Hospital, Korea University College of Medicine, Seoul 152-703, Korea.
4. Department of Gastroenterologic Surgery, Korea University Guro Hospital, Korea University College of Medicine, Seoul 152-703, Korea.
5. Department of Radiology, Kyung Hee University Medical Center, Seoul 130-872, Korea.
6. Division of Interventional Radiology, Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO 63110, USA.