1. Research Institute of Biomedical Engineering, College of Medicine, The Catholic University of Korea, Seoul, Korea.
2. Department of Radiation Oncology, Seoul National University Bundang Hospital, Seongnam, Korea.
3. Department of Radiation Oncology, Kunkuk University Medical Center, Seoul, Korea.
4. Department of Radiation Oncology, Seoul Metropolitan Government Seoul National University Boramae Medical Center, Seoul, Korea.