1. Department of Pediatrics and Child Health, Kurume University School of Medicine, 67 Asahi-machi, Kurume, Fukuoka 830-0011, Japan
2. Pattern Processing Lab, School of Computer Science and Engineering, The University of Aizu, Fukushima 965-8580, Japan
3. School of Computer Science and Engineering, The University of Aizu, Fukushima 965-8580, Japan
4. Faculty of Humanities and Social Sciences, Kumamoto University, Kumamoto 860-8555, Japan