1. Section of Radiation Safety and Quality Assurance, National Cancer Center Hospital , 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045, Japan
2. Department of Radiation Oncology, Juntendo University Graduate School of Medicine , 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan
3. Department of Radiological Sciences, Graduate School of Human Health Sciences, Tokyo Metropolitan University , 7-2-10 Higashi-ogu, Arakawa-ku, Tokyo 116-8551, Japan
4. Department of Radiological Technology Radiological Oncology, National Cancer Center Hospital , 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045, Japan
5. Department of Medical and Dental Sciences, Graduate School of Biomedical Sciences, Nagasaki University , 1-12-4 Sakamoto, Nagasaki city, Nagasaki, 852-8523, Japan
6. Department of Radiation Oncology, National Cancer Center Hospital , 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045, Japan