1 Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul National University Hospital, Republic of Korea.
2 Department of Radiology, Seoul Metropolitan Government Seoul National University Boramae Medical Center, Republic of Korea.
3 Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul Metropolitan Government Seoul National University Boramae Medical Center, Republic of Korea.
4 Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Seoul Metropolitan Government Seoul National University Boramae Medical Center, Republic of Korea. Electronic address: heechung@snu.ac.kr.