1. The Second Affiliated Hospital of Shandong First Medical University, Taian, China
2. Ultrasound, Jinan Maternal and Child Health Care Hospital, Jinan, China
3. Ultrasound, Qilu Hospital of Shandong University, Jinan, China
4. Ultrasound, The Third Affiliated Hospital of Shandong First Medical University (Affiliated Hospital of Shandong Academy of Medical Sciences), China