1. Department of Radiotherapythe Second Hospital of Jilin University Changchun 130041 P. R. China
2. Key Laboratory of Polymer EcomaterialsChangchun Institute of Applied ChemistryChinese Academy of Sciences Changchun 130022 P. R. China
3. Jilin Biomedical Polymers Engineering Laboratory Changchun 130022 P. R. China
4. Department of Hepatobiliary and Pancreatic Surgerythe Second Hospital of Jilin University Changchun 130041 P. R. China