1. Graduate School of Biomedical Science and Engineering Hokkaido University Sapporo Japan
2. Faculty of Engineering Hokkaido University Sapporo Japan
3. Department of Medical Physics Hokkaido University Hospital Sapporo Japan
4. Proton Beam Therapy Center Hokkaido University Hospital Sapporo Japan
5. Department of Radiation Oncology Faculty and Graduate School of Medicine Hokkaido University Sapporo Japan
6. Research and Development GroupHitachiLtd. Hitachi‐shiJapan