1. Biomedical Imaging Research Center, University of Fukui, Fukui 910-1193, Japan
2. Department of Radiology, Kobe University Hospital, Kobe 650-0017, Japan
3. Department of Radiology, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan
4. First Department of Surgery, Faculty of Medical Sciences, University of Fukui, Fukui 910-1193, Japan