1. Department of Ultrasonography, Jining Maternal and Child Health Family Planning Service Center, Jining, Shandong 272000, P.R. China
2. Department of Ultrasonography, Jiaxiang People's Hospital, Jining, Shandong 272400, P.R. China
3. Department of Ultrasonography, Jining No. 1 People's Hospital, Jining, Shandong 272011, P.R. China
4. Department of Internal Medicine Ward, Zhangqiu People's Hospital, Jinan, Shandong 250200, P.R. China
5. Department of Cardiology, Zhangqiu People's Hospital, Jinan, Shandong 250200, P.R. China