1. Department of Physics, Iwate Medical University, 1-1-1 Idaidori, Yahaba, Iwate 028-3694, Japan
2. Department of Radiology, School of Medicine, Iwate Medical University, 2-1-1 Idaidori, Yahaba, Iwate 028-3694, Japan
3. Department of Surgery, Toho University Ohashi Medical Center, 2-22-36 Ohashi, Meguro, Tokyo 153-8515, Japan