1. Department of Medical Physics and Engineering, Osaka University Graduate School of Medicine, 1–7 Yamadaoka, Suita-shi, Osaka, 565-0871, Japan
2. National Institutes for Quantum and Radiological Science and Technology, 4-9-1 Anagawa, Inage-ku, Chiba 263-8555, Japan
3. Osaka Heavy Ion Therapy Center, 3-1-10 Otemae, Chuo-ku, Osaka-shi, Osaka, 540-0008, Japan
4. Department of Radiation Oncology, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita-shi, Osaka, 565-0871, Japan