1. Department of Radiation Oncology National Cancer Center Hospital Tokyo Japan
2. Shin‐Matsudo Accuracy Radiation Therapy Center Shin‐Matsudo Central General Hospital Chiba Japan
3. Department of Diagnostic Pathology National Cancer Center Hospital Tokyo Japan
4. Department of Diagnostic Radiology National Cancer Center Hospital Tokyo Japan
5. Department of Head and Neck Surgery National Cancer Center Hospital Tokyo Japan
6. Department of Head and Neck, Esophageal Medical Oncology National Cancer Center Hospital Tokyo Japan
7. Radiation Safety and Quality Assurance Division National Cancer Center Hospital Tokyo Japan