1. Proton Therapy Center; Sapporo Teishinkai Hospital; Sapporo Hokkaido Japan
2. Department of Radiology; Hyogo Ion Beam Medical Center; Tatsuno Hyogo Japan
3. Department of Radiation Oncology; Hakodate Goryoukaku Hospital; Hakodate Hokkaido Japan
4. Department of Radiology; Uji-Tokushukai Medical Center; Uji Kyoto Japan
5. Department of Biostatistics; Hyogo College of Medicine; Nishinomiya Hyogo Japan
6. Center for Radiation Oncology; Dokkyo Medical University; Shimotsuga-gun Tochigi Japan