1. Department of Radiology, College of Medicine Seoul National University and The Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul 110-744, Korea.
2. Department of Pathology, College of Medicine Seoul National University and The Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul 110-744, Korea.
3. Department of Radiology, Boramae Municipal Hospital, Seoul 156-707, Korea.