1. Department of Radiation Physics and Technology, Southern Tohoku Proton Therapy Center, Koriyama, Japan
2. Department of Radiological Life Sciences, Division of Medical Life Sciences, Hirosaki University Graduate School of Health Sciences, Hirosaki, Aomori, Japan
3. Preparing Section for New Faculty of Medical Science, Fukushima Medical University, Fukushima, Fukushima, Japan
4. Departmentof Radiation Oncology, Southern Tohoku Proton Therapy Center, Koriyama, Japan