1. Department of Radiology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Institute of Radiation Medicine, Seoul National University Medical Research Center, Seongnam 13620, Korea.
2. Department of Radiology, SMG-SNU Boramae Medical Center, Seoul 07061, Korea.
3. Department of Radiology, Seoul National University Hospital, Seoul National University College of Medicine, Seoul 03080, Korea.
4. Department of Radiology, University of Pittsburgh Medical Center, Pittsburgh, PA 15213, USA.