1. Department of Obstetrics and Gynecology, Yokohama City Seibu Hospital, St. Marianna University School of Medicine, Kawasaki, Japan
2. Department of Radiology, Yokohama City Seibu Hospital, St. Marianna University School of Medicine, Kawasaki, Japan
3. Department of Obstetrics and Gynecology, St. Marianna University School of Medicine, Kawasaki, Japan