1. Department of Otorhinolaryngology Head and Neck Surgery Graduate School of Biomedical and Health Sciences, Hiroshima University Hiroshima Japan
2. Department of Gastrointestinal Endoscopy and Medicine Hiroshima University Hospital Hiroshima Japan
3. Department of Endoscopy Hiroshima University Hospital Hiroshima Japan
4. Center for Medical Education Institute of Biomedical & Health Sciences Hiroshima University Hiroshima Japan