1. Veterinary Medical Center, Osaka Prefecture University, 1-58 Rinku Ourai Kita, Izumisano-shi, Osaka 598-8531, Japan
2. Laboratory of Veterinary Radiology, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-58 Rinku Ourai Kita, Izumisano-shi, Osaka 598-8513, Japan