1. Faculty of Graduate Studies, Shanxi Medical University, Taiyuan, Shanxi 030000, P.R. China
2. Department of Gastroenterology, The First Hospital of Shanxi Medical University, Taiyuan, Shanxi 030000, P.R. China
3. Endoscopy Center, Shanxi Cancer Hospital, Taiyuan, Shanxi 030000, P.R. China