1. Department of Internal Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
2. Department of Pulmonary and Critical Care Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
3. Department of Family Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
4. Department of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.