1. Department of Radiation Oncology, Nagoya Proton Therapy Center, Nagoya City West Medical Center, Nagoya, Aichi 462‑8508, Japan
2. Department of Diagnostic Radiology, Nagoya City West Medical Center, Nagoya, Aichi 462‑8508, Japan
3. Division of Cancer Biology, Aichi Cancer Center Research Institute, Nagoya, Aichi 464‑8681, Japan
4. Department of Radiology, Nagoya City University Graduate School of Medical Sciences, Nagoya, Aichi 467‑8601, Japan