1. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, The Catholic University of Korea College of Medicine, Seoul, Korea.
2. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Armed Forces Capital Hospital, Seongnam, Korea.
3. Department of Radiology, Chonnam National University Hospital, Gwangju, Korea.
4. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Wonkwang University Sanbon Hospital, Wonkwang University College of Medicine, Gunpo, Korea.