1. Department of Gastrointestinal Endoscopy, NTT Medical Center Tokyo, Tokyo, Japan
2. Department of Gastrointestinal Endoscopy, Yokohama Sakae Kyosai Hospital, Yokohama, Japan
3. Department of Gastroenterology and Hepatology, Kyorin University School of Medicine, Tokyo, Japan
4. Department of Gastroenterology, Keiyu Hospital, Tokyo, Japan
5. Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
6. Department of Gastroenterology, Omori Red Cross Hospital, Tokyo, Japan