1. Department of Radiology Huashan Hospital Fudan University Shanghai 200040 P. R. China
2. Department of Materials Science Fudan University Shanghai 200433 P. R. China
3. Tongji University Cancer Center Shanghai Tenth People's Hospital Tongji University School of Medicine Shanghai 200072 P. R. China
4. State Key Laboratory of High Performance Ceramics and Superfine Microstructure Shanghai Institute of Ceramics Chinese Academy of Sciences Shanghai 200050 P. R. China
5. Department of Radiology Renji Hospital School of Medicine Shanghai Jiao Tong University Shanghai 200127 P. R. China