1. Division of Research and Development for Minimally Invasive Treatment, Cancer Center, Keio University School of Medicine, Tokyo, Japan
2. Division of Gastroenterology and Hepatology, Department of Internal Medicine, Keio University School of Medicine, Tokyo, Japan
3. Medical Education Center, Keio University School of Medicine, Tokyo, Japan
4. Center for Diagnostic and Therapeutic Endoscopy, Keio University School of Medicine, Tokyo, Japan