1. Department of Special Inspection, Qingdao Women and Children's Hospital, Qingdao City, Shandong Province, China
2. Department of Cardiac Ultrasound, Affiliated Hospital of Qingdao University, Qingdao City, Shandong Province, China
3. Department of Ultrasound, Weifang People's Hospital, Weifang City, Shandong Province, China
4. Department of Ultrasound, Affiliated Hospital of Qingdao University, Qingdao City, Shandong Province, China
5. Department of Abdominal Ultrasound, Affiliated Hospital of Qingdao University, Qingdao City, Shandong Province, China