1. Department of Biomedical Engineering, College of Medicine, The Catholic University of Korea, Seoul, Korea.
2. Department of Radiation Oncology, Presbyterian Medical Center of Korea, Jeonju, Korea.
3. Department of Radiation Oncology, Bucheon St. Mary's Hospital, The Catholic University of Korea, Bucheon, Korea.
4. Department of Radiation Oncology, Incheon St. Mary's Hospital, The Catholic University of Korea, Incheon, Korea.
5. Department of Medical Physics, Kyonggi University of Korea, Suwon, Korea.