1. Department of Radiology, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, Korea.
2. Department of Occupational and Environmental Medicine, Inha University College of Medicine, Incheon, Korea.
3. Department of Preventive Medicine, Dong-A University Collage of Medicine, Busan, Korea.
4. Department of Occupational and Environmental Medicine, Kosin University College of Medicine, Busan, Korea.
5. Total Health Care Center, Kangbuk Samsung Hospital, School of Medicine, Sungkyungkwan University, Seoul, Korea.
6. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, National Medical Center, Seoul, Korea.
7. Department of Occupational and Environmental Medicine, Ulsan University Hospital, University of Ulsan College of Medicine, Ulsan, Korea.