[1] Chongqing Med Univ, Childrens Hosp, Natl Clin Res Ctr Child Hlth & Disorders, Dept Clin Epidemiol & Biostat,Minist Educ,Key Lab, Chongqing 400016, Peoples R China
[2] Chongqing Med Univ, Childrens Hosp, Ultrasound Dept, Chongqing 400014, Peoples R China
[3] Chongqing Med Univ, Childrens Hosp, Natl Clin Res Ctr Child Hlth & Disorders, Dept Clin Epidemiol & Biostat,Minist Educ,Key Lab, 136 2nd St, Chongqing 400016, Peoples R China