1. Department of Gynecology, Liuzhou Maternity and Child Healthcare Hospital, Liuzhou, Guangxi, China
2. State Key Laboratory of Ultrasound in Medicine and Engineering, Chongqing Medical University, Chongqing, China
3. Department of Obstetrics and Gynecology, The Fourth Affiliated Hospital of Guangxi Medical University, Liuzhou, Guangxi, China