1. Division of Research and Development for Minimally Invasive Treatment, Cancer Center, Keio University School of Medicine, Shinjuku-ku, Japan
2. Center for Diagnostic and Therapeutic Endoscopy, Keio University School of Medicine, Shinjuku-ku, Japan
3. Division of Gastroenterology and Hepatology, Department of Internal Medicine, Keio University School of Medicine, Shinjuku-ku, Japan
4. Department of Otolaryngology, Head and Neck Surgery, Keio University School of Medicine, Shinjuku-ku, Japan