1. Department of Gynecology, Liuzhou Maternity and Child Healthcare Hospital, Liuzhou Guangxi, P. R. China
2. Jincheng Hospital Affiliated to Changzhi Medical College, Jincheng People’s Hospital, Shanxi, China
3. State Key Laboratory of Ultrasound in Medicine and Engineering, College of Biomedical Engineering, Chongqing Medical University, Chongqing, China