1. Department of Surgery, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
2. Division of Biostatistics, Center for Medical Research and Information, Asan Medical Center, University of Ulsan College of Medicine, Seoul, Korea.
3. Biomedical Research Center, Asan Institute for Life Sciences, Asan Medical Center, Seoul, Korea.
4. Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Seoul, Korea.