1. Department of Radiology and Institute of Radiation Medicine, Seoul National University College of Medicine, Clinical Research Institute, Seoul 110-744, Korea.
2. Department of Radiology, Seoul National University Boramae Hospital, Seoul 156-707, Korea.
3. Department of Radiology, National Cancer Center, Goyang 410-769, Korea.
4. Department of Surgery, Seoul National University College of Medicine, Seoul 110-744, Korea.
5. Department of Radiology, Gachon University Gil Medical Center, Incheon 405-760, Korea.