1. Departments of Radiology, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba 271-8587, Japan
2. Histology, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba 271-8587, Japan
3. Laboratory for Electron Beam Research and Application(LEBRA), Institute of Quantum Science, Funabashi Campus of College of Science and Technology, Nihon University, Funabashi, Chiba 274-8501, Japan
4. Nihon University Graduate School of Dentistry at Matsudo, Oral Radiology, Matsudo, Chiba 271-8587, Japan