1. Department of Pediatrics; Yokohama City University Graduate School of Medicine; Kanazawa-ku Yokohama City Japan
2. Center for Clinical Epidemiology; St. Luke's International University; Chuo-ku Tokyo Japan
3. Department of Pediatrics; Saiseikai Yokohama-Shi Nanbu Hospital; Kounan-ku Yokohama City Japan
4. Department of Radiology; Kanagawa Children's Medical Center; Minami-ku Yokohama City Japan
5. Department of Hematology and Oncology; Kanagawa Children's Medical Center; Minami-ku Yokohama City Japan