1. Gunma University Heavy Ion Medical Center, Gunma, Japan;
2. Department of Radiation Oncology, Nara Medical University, Nara, Japan;
3. Department of Oral and Maxillofacial Surgery, Nara Medical University, Nara, Japan;
4. Department of Drug Discovery and Biomedical Sciences, South Carolina College of Pharmacy, University of South Carolina, Columbia, SC, USA