1. Department of Radiology and the Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul 138-736, Korea.
2. Department of Thoracic and Cardiovascular Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul 138-736, Korea.
3. Department of Neonatology, Asan Medical Center, University of Ulsan College of Medicine, Seoul 138-736, Korea.