1. Department of Radiology, Bundang Jesaeng General Hospital, Sungnam 463-774, Korea.
2. Department of Radiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul 135-710, Korea.
3. Division of Pulmonology, Department of Internal Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul 135-710, Korea.