1. Department of Otorhinolaryngology, Head and Neck Surgery, Graduate School of Medicine, University of the Ryukyus, Nishihara-cho, Japan
2. Department of Otorhinolaryngology-Head and Neck Surgery, University of Miyazaki, Miyazaki, Japan
3. Department of Radiology, Graduate School of Medicine, University of the Ryukyus, Nishihara-cho, Japan
4. Department of Radiology, Yokohama City University School of Medicine, Yokohama, Japan