1. Biomaterials Research Center, Korea Institute of Science and Technology, P. O. Box 131, Cheongryang, Seoul 130-650, Korea, Department of Chemical Engineering Sungkyunkwan University, Suwon, Korea
2. Biomaterials Research Center, Korea Institute of Science and Technology, P. O. Box 131, Cheongryang, Seoul 130-650, Korea
3. Department of Chemical Engineering Sungkyunkwan University, Suwon, Korea
4. Biomaterials Research Center, Korea Institute of Science and Technology, P. O. Box 131, Cheongryang, Seoul 130-650, Korea,
5. Future Convergence Technology Labaratory, Korea Institute of Science and Technology, Seoul, Korea
6. Department of Radiology, Asan Hospital, Seoul, Korea