1. State Key Laboratory of Ultrasound in Medicine and Engineering, College of Biomedical Engineering, Chongqing Medical University, Chongqing, China
2. Department of Gynecology, Liuzhou Maternity and Child Healthcare Hospital, Liuzhou, Guangxi, P. R. China
3. Department of Prevention and Protection, Liuzhou Maternity and Child Healthcare Hospital, Liuzhou, Guangxi, P. R. China
4. School of Public Health, Chongqing Medical University, Chongqing, China