1. Department of Hepatobiliary Surgery; Eastern Hepatobiliary Surgery Hospital; Second Military Medical University; Shanghai 200438 P. R. China
2. State Laboratory of High Performance Ceramics and Superfine Microstructure; Shanghai Institute of Ceramics; Chinese Academy of Sciences; Shanghai 200050 P. R. China
3. Department of Ultrasound; The Affiliated People's Hospital of Jiangsu University; Zhenjiang 212002 P. R. China