1. Department of Radiation Oncology, Shiga General Hospital , 5-4-30 Moriyama, Moriyama-shi 524-8524, Shiga , Japan
2. Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University , 54 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507 , Japan
3. Division of Medical Physics , Department of Information Technology and Medical Engineering, Human Health Sciences, , 53 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507 , Japan
4. Graduate School of Medicine, Kyoto University , Department of Information Technology and Medical Engineering, Human Health Sciences, , 53 Kawahara-cho, Shogoin, Sakyo-ku, Kyoto 606-8507 , Japan