1. Department of Radiology, Saitama Children's Medical Center, 1-2 Shintoshin Chuo-ku Saitama, Saitama, 330-8777 Japan.
2. Department of Radiology, Keio University School of Medicine, Tokyo, Japan.
3. Department of Diagnostic and Interventional Radiology, University of Tsukuba Hospital, Tsukuba, Japan.
4. Department of Pediatrics, Saitama City Hospital, Saitama, Japan.