1. Department of Veterinary Surgery, College of Veterinary Medicine, Seoul National University, Seoul 151-742, Korea.
2. Department of Veterinary Radiology, College of Veterinary Medicine, Seoul National University, Seoul 151-742, Korea.
3. Laboratory of Stem Cell and Tumor Biology, Department of Veterinary Public Health, College of Veterinary Medicine, Seoul National University, Seoul 151-742, Korea.