* Corresponding authors

^a Department of General Surgery, The Second Hospital of Jilin University, 218 Ziqiang Street, Changchun, Jilin 130000, P. R. China
E-mail: ztzrh0319@163.com

^b Department of Gastrointestinal Colorectal and Anal Surgery, China-Japan Union Hospital of Jilin University, 126 Xiantai Street, Changchun, Jilin 130033, P. R. China

^c 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
E-mail: leiwang@ciac.ac.cn
Fax: +86 431 85262779
Tel: +86 431 85262779

^d University of Chinese Academy of Sciences, Beijing 100049, P. R. China

^e Department of Radiology, China-Japan Union Hospital of Jilin University, 126 Xiantai Street, Changchun, Jilin 130033, P. R. China