1. Department of Ultrasound, Sichuan Provincial Hospital for Women and Children, Chengdu, Sichuan 610031, P.R. China
2. Department of Pathology, Sichuan Provincial Hospital for Women and Children, Chengdu, Sichuan 610031, P.R. China
3. Department of Gynaecology, Sichuan Provincial Hospital for Women and Children, Chengdu, Sichuan 610031, P.R. China
4. Department of Ultrasound, Sichuan Provincial People's Hospital, University of Electronic Science and Technology of China, Chengdu, Sichuan 611731, P.R. China