1. Radiation Oncology, Clinical Medicine, Faculty of Medicine, University of Tsukuba, Tsukuba, 305-8575, Japan
2. Department of Basic Medical Sciences for Radiation Damages, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba, 263-8555, Japan
3. Department of Charged Particle Therapy Research, Clinical Research Cluster, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba, 263-8555, Japan
4. Department of Accelerator and Medical Physics, National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Chiba, 263-8555, Japan
5. Medicine & Biology Division, Heavy Ion Medical Center, Gunma University, Gunma, 371-8511, Japan