1. Department of Medical System Engineering, Graduate School of Engineering, Chiba University
2. Center for Frontier Medical Engineering, Chiba University, Chiba, Japan
3. Department of Frontier Surgery, Graduate School of Medicine, Chiba University, Chiba, Japan
4. Department of Gastroenterology, Foundation for Detection of Early Gastric Carcinoma, Tokyo, Japan
5. Department of Information Processing and Computer Science, Graduate School of Advanced Integration Science, Chiba University, Chiba, Japan