1. Department of General Ultrasound, First Hospital of Qinhuangdao, Qinhuangdao, Hebei, China (mainland)
2. Department of Doppler Ultrasound, First Hospital of Qinhuangdao, Qinhuangdao, Hebei, China (mainland)
3. Department of Obstetrics and Gynecology, First Hospital of Qinhuangdao, Qinhuangdao, Hebei, China (mainland)
4. Department of General Surgery, First Hospital of Qinhuangdao, Qinhuangdao, Hebei, China (mainland)