1. Department of Radiology, International University of Health and Welfare, Mita Hospital, Otawara, Japan
2. Department of Radiology, Institute of Medical Science, University of Tokyo, Tokyo, Japan
3. The Head and Neck Oncology Center, International University of Health and Welfare, Mita Hospital, Otawara, Japan
4. Department of Pathology, International University of Health and Welfare, School of Medicine, Otawara, Japan