1. Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, 88 Olympic-ro 43 Gil, Songpa-gu, Seoul 138-736, Korea.
2. Department of Cardiothoracic Surgery, University of Ulsan College of Medicine, Asan Medical Center, Seoul, South Korea.
3. Department of Medical Statistics, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.