1. Division of Veterinary Radiology, Department of Veterinary Science, Nippon Veterinary and Life Science University, 1–7–1 Kyounan-cho, Musashino-shi, Tokyo 180–8602, Japan
2. Department of Veterinary Pathology, The University of Tokyo, 1–1–1 Yayoi, Bunkyo-ku, Tokyo 113–8657, Japan
3. The Animal Medical Center, Department of Veterinary Science, Nippon Veterinary and Life Science University, 1–7–1 Kyounan-cho, Musashino-shi, Tokyo 180–8602, Japan