1. Department of Radiology, SMG-SNU Boramae Medical Center, Seoul, Korea.
2. Department of Radiology, Seoul National University College of Medicine, Seoul, Korea.
3. Department of Radiology, Seoul National University Hospital, Seoul, Korea.
4. Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Korea.
5. Department of Radiology and Research Institute of Radiological Science, Severance Hospital, Yonsei University College of Medicine, Seoul, Korea.