1. Department of Radiology and Research Institute of Radiology, Asan Medical Center, University of Ulsan College of Medicine, Seoul 138-736, Korea.
2. Korea Institute of Science and Technology, Biomedical Research Center, Seoul 136-791, Korea.
3. Department of Nuclear Medicine, Asan Medical Center, University of Ulsan College of Medicine, Seoul 138-736, Korea.
4. Department of Radiology, Division of Musculoskeletal Imaging, Stanford University School of Medicine, Stanford, CA 94305, USA.