1. Laboratory of Anatomy, Department of Biomedical Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
2. Laboratory of Experimental Animal Science, Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
3. Department of Veterinary Radiology, School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Hokkaido, Japan