1. Racehorse Hospital, Miho Training Center, Japan Racing Association, Ibaraki 300-0493, Japan
2. Racehorse Hospital, Ritto Training Center, Japan Racing Association, Shiga 520-3085, Japan
3. Equine Research Institute, Japan Racing Association, Tochigi 329-0412, Japan
4. Laboratory of Veterinary Radiology, School of Veterinary Medicine, Azabu University, Kanagawa 252-5201, Japan