1. Department of Health Sciences Graduate School of Medical Sciences Kyushu University 3‐1‐1 Maidashi, Higashi‐ku Fukuoka City Fukuoka 812‐8582 Japan
2. Department of Radiology Harasanshin Hospital 1‐8 Taihakumachi, Hakata‐ku Fukuoka City Fukuoka 812‐0033 Japan
3. Department of Radiation Oncology Hamamatsu University School of Medicine 1‐20‐1 Handayama, Higashi‐ku Hamamatsu City Shizuoka 431‐3192 Japan
4. Department of Health Sciences Faculty of Medical Sciences Kyushu University 3‐1‐1 Maidashi, Higashi‐ku Fukuoka City Fukuoka 812‐8582 Japan