1. Department of Radiology and the Research Institute of Radiology, University of Ulsan, College of Medicine, Asan Medical Center, Seoul 138-736, Korea.
2. Department of Radiology, Soonchunhyang University Hospital, Seoul 140-743, Korea.
3. Department of Radiology, East-West Neomedical Center, Kyunghee University, College of Medicine, Seoul 134-090, Korea.
4. Department of Mechanical Engineering, Dankook University, Gyeonggi-do 448-701, Korea.
5. School of Mechanical and Automotive Engineering, University of Ulsan, Ulsan 680-749, Korea.
6. Department of Neurology, University of Ulsan, College of Medicine, Asan Medical Center, Seoul 138-736, Korea.