1. Department of Radiology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, Korea.
2. Department of Internal Medicine, Chungbuk National University Hospital, Division of Pulmonary and Critical Care Medicine, Cheongju, Korea.
3. Department of Radiology, Konkuk University Medical Center, Seoul, Korea.
4. Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul, Korea.