1. Department of Radiology; Graduate School of Comprehensive Human Sciences, University of Tsukuba; Tsukuba, Ibaraki; Japan
2. Department of Radiology; Faculty of Medicine, University of Tsukuba; Tsukuba, Ibaraki; Japan
3. Department of Radiological Technology; Saitama Children's Medical Center; Saitama, Saitama; Japan
4. Department of Radiology; Tsukuba University Hospital; Tsukuba, Ibaraki; Japan
5. Department of Epidemiology; Faculty of Medicine, University of Tsukuba; Tsukuba, Ibaraki; Japan