1. Department of Radiology, Keio University School of Medicine, Shinjuku-ku, Tokyo, Japan
2. Department of Radiology, Nippon Koukan Hospital, Kawasaki-shi, Kanagawa, Japan
3. Department of Radiology, National Defense Medical College, Tokorozawa-shi, Saitama, Japan
4. Department of Gastroenterology and Hepatology, Nippon Koukan Hospital, Kawasaki-shi, Kanagawa, Japan