1. Department of Ultrasound the Third People's Hospital of Chengdu City the Affiliated Hospital of Southwest Jiaotong University Chengdu 600031 P. R. China
2. Institute of Ultrasound Imaging and Department of Ultrasound Second Affiliated Hospital of Chongqing Medical University Chongqing 400010 P. R. China
3. Department of Ultrasound Hainan General Hospital Haikou 570311 P. R. China
4. State Key Lab of High Performance Ceramics and Superfine Microstructure Shanghai Institute of Ceramics Chinese Academy of Sciences Shanghai 200050 P. R. China