1. Department of Radiation Oncology; Graduate School of Biomedical & Health Sciences; Hiroshima University; 1-2-3 Kasumi, Minami-ku Hiroshima 734-8551 Japan
2. Department of Radiation Oncology; Tokyo Women's Medical University; 8-1 Kawada-cho, Shinjuku-ku Tokyo 162-8666 Japan
3. Department of Medical Physics; Graduate School of Medicine; Tokyo Women's Medical University; 8-1 Kawada-cho, Shinjuku-ku Tokyo 162-8666 Japan
4. Department of Radiation Oncology; Hiroshima University Hospital; 1-2-3 Kasumi, Minami-ku Hiroshima 734-8551 Japan
5. Department of Nuclear Engineering and Management; School of Engineering; The University of Tokyo; 7-3-1 Hongo, Bunkyo-ku Tokyo 113-8656 Japan
6. Department of Radiology; Kyoto Prefecture University of Medicine; 465 Kajii-cho, Kawaramachi-Hirokoji, Kamigyo-ku Kyoto 602-8566 Japan
7. Hiroshima High-Precision Radiotherapy Cancer Center; 2-2 Hutabanosato, Higashi-ku Hiroshima 732-0057 Japan