1. Department of Special Inspection, Shandong Qingdao Hospital of Integrated Traditional and Western Medicine, Qingdao, Shandong 266002, P.R. China
2. Department of Ultrasound, Qingdao Fuwai Cardiovascular Hospital, Qingdao, Shandong 266021, P.R. China
3. Department of Ultrasound Medicine, The Third People's Hospital of Qingdao, Qingdao, Shandong 266041, P.R. China
4. Department of Special Inspection, Qingdao Women and Children's Hospital, Qingdao, Shandong 266000, P.R. China