1. Division of Otolaryngology, Tohoku Medical and Pharmaceutical University, Sendai 981-0905, Japan
2. Division of Pathology, Tohoku Medical and Pharmaceutical University, Sendai 981-0905, Japan
3. Division of Anatomy and Cell Biology, Tohoku Medical and Pharmaceutical University, Sendai 981-0905, Japan
4. Division of Radiology, Tohoku Medical and Pharmaceutical University, Sendai 981-0905, Japan