1. Department of Radiation Oncology, Kyung Hee University Hospital at Gandong, Seoul, Korea.
2. Department of Bio-convergence Engineering, Korea University, Seoul, Korea.
3. Department of Radiation Oncology, Kyung Hee University Medical Center, Seoul, Korea.
4. Department of Radiation Oncology, Samsung Medical Center, Seoul, Korea.
5. Proton Therapy Center, National Cancer Center, Goyang, Korea.