1. Department of Radiology, Seoul National University College of Medicine, Seoul 110-744, Korea.
2. Department of Radiology, Keimyung University College of Medicine, Dongsan Medical Center, Daegu 700-712, Korea.
3. Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul 110-744, Korea.
4. Kidney Research Institute, Seoul National University Medical Research Center, Seoul 110-744, Korea.