1. Department of Pediatric Surgery, The University of Tokyo Hospital, Tokyo, Japan.
2. Department of Pediatric Surgery, Gunma Children's Medical Center, Shibukawa, Gunma, Japan.
3. Department of Pediatric Surgery, Saitama Children's Medical Center, Saitama, Japan.
4. Department of Mechanical Engineering, School of Engineering, The University of Tokyo, Tokyo, Japan.
5. Department of Pediatric Surgery, Nagoya University Graduate School of Medicine, Nagoya, Aichi, Japan.