1. Department of Radiology, China−Japan Union Hospital of Jilin University, 126 Xiantai Street, Changchun, Jilin 130033, P. R. China
2. State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, 5625 Renmin Street, Changchun, Jilin 130022, P. R. China
3. University of Science and Technology of China, Hefei, Anhui 230026, P. R. China
4. Department of Gastrointestinal Colorectal and Anal Surgery, China−Japan Union Hospital of Jilin University, 126 Xiantai Street, Changchun, Jilin 130033, P. R. China