1. Department of Radiology, Guangdong Provincial Key Laboratory of Major Obstetric Diseases, Guangdong Provincial Clinical Research Center for Obstetrics and Gynecology, The Third Affiliated Hospital of Guangzhou Medical University, Guangzhou 510150, China
2. School of Automation, Guangdong University of Technology, Guangzhou 510006, China
3. School of physics, electronics and electrical engineering, Xiangnan University, Chenzhou 423000, China