1. Department of Radiation Oncology, Kobe Proton Center, Kobe, Hyogo 650‑0047, Japan
2. Division of Radiation Therapy, Radiation and Proton Therapy Center, Shizuoka Cancer Center, Shizuoka, Shizuoka 411‑8777, Japan
3. Division of Medical Physics, Kobe Proton Center, Kobe, Hyogo 650‑0047, Japan
4. Department of Anesthesiology, Kobe Proton Center, Kobe, Hyogo 650‑0047, Japan