1. Department of Radiology, Armed Force Byukjae Hospital, Gyeonggi-do 412-510, Korea.
2. Department of Radiology, Seoul National University College of Medicine, and Institute of Radiation Medicine, Seoul National University Medical Research Center, Seoul 110-744, Korea.
3. Department of Family Medicine, Armed Force Byukjae Hospital, Gyeonggi-do 412-510, Korea.
4. Department of Family Medicine, Gangneung Asan Hospital, Ulsan University College of Medicine, Gangwon-do 210-711, Korea.
5. Department of Internal Medicine, Armed Force Byukjae Hospital, Gyeonggi-do 412-510, Korea.
6. Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine and Lung Institute, Seoul National University College of Medicine, Seoul 110-744, Korea.
7. Department of Family Medicine, Chungnam National University School of Medicine, Daejeon 301-721, Korea.