1. Department of Radiology, School of Medicine, Iwate Medical University, 2-1-1 Idaidori, Yahaba, Iwate 028-3695, Japan
2. Department of Physics, Iwate Medical University, 1-1-1 Idaidori, Yahaba, Iwate 028-3694, Japan
3. Department of Radiation Oncology, Iwate Medical University Hospital, Iwate Medical University, 2-1-1 Idaidori, Yahaba, Iwate 028-3695, Japan