Objective: To explore the value of prenatal MRI for predicting prognosis after balloon occlusion of abdominal aorta-assisted cesarean section (AABC-CS) in patients with placenta accreta. Methods: Prenatal MRI of 86 patients underwent AABC-CS due to placenta accreta were reviewed retrospectively. According to the prognosis, the patients were divided into good prognosis group (intraoperative blood loss <1 000 ml and unremoved uterus, n=50) and poor prognosis group (intraoperative blood loss ≥1 000 ml or uterus removed, n=36). MRI signs between the 2 groups were compared, and multivariate Logistic regression analysis was used to obtain the risk factors for predicting poor prognosis, and the predictive efficacy was calculated. Results: MRI signs of abnormal intraplacental vascularity, hypointense intraplacental bands, uterine recess, placenta percreta were significantly more common in poor prognosis group (all P<0.001). Multivariate Logistic regression analysis showed that abnormal intraplacental vascularity (odds ratio [OR]=15.78, P=0.015) and placenta percreta (OR=12.25, P=0.020) were risk factors for poor prognosis, with sensitivity and specificity of 77.78% (28/36), 62.00% (31/50) and 44.44% (16/36), 100% (50/50), respectively. Conclusion: Prenatal MRI signs of abnormal intraplacental vascularity and placenta percreta might be the predictors of intraoperative significant hemorrhage and hysterectomy after AABC-CS in patients with placenta accreta.

Objective To compare the diagnostic value of MR examination with fast imaging employing steady state acquisition (FIESTA) and single shot fast spin echo (SSFSE) sequences for normal fetal thymuses.Methods Totally 366 normal fetuses were examined using MRI with FIESTA and SSFSE sequences,and the anatomy and MR manifestations of thymuses were observed.Kappa analysis and x2 test were performed.The transverse area (TA) and transverse diameter (TD) were measured on the "three vessel" level,while the superoinferior diameter (SID) was measured on the sagittal level.The mean value of these parameters at different gestational were calculated,and the regression equations of each parameter and gestational age were fitted.Results Two doctors had good agreements with the images of FIESTA and SSFSE sequences (Kappa=0.745,0.802,both P＜0.01).The clear rate of FIESTA and SSFSE sequences was 86.34％ (632/732) and 37.70％ (276/732) respectively,and the differences were significant (x2 =367.520,P＜0.001).The thymic size increased with the gestational age,and the regression equations and correlation coefficients were:TA =-5.80 + 0.35 ×gestational (r=0.820,P＜0.01),TD=-14.59+1.63×gestational (r=0.817,P＜0.01),and SID=-9.63+1.44×gestational (r=0.778,P＜0.01).Conclusion The subtle structure and contour of fetal thymus showed with FIESTA sequence are clearer than those of SSFSE sequence.MRI can clearly show fetal thymus after 22 weeks of pregnancy.

Objective To explore the value of prenatal MRI signs in diagnosis of placenta accreta.Methods MRI data of 163 pregnant women with suspected placenta accreta were retrospectively reviewed.According to the results of cesarean section,they were divided into placenta accreta group (n =136) or without placenta accreta group (n =27).The differencesof MRI signs between the two groups were compared.Taking cesarean section results as the gold standard,the sensitivity,specificity,positive and negative predictive value of MRI signs were calculated,respectively.Results Uterine bulging,abnormal vessels and hypointense T2WI bands at junction of placental and myometrium,as well as uterine recess had statistical differences between the two groups (all P＜0.05).No statistical difference of placental heterogeneity,focal interruptions in myometrial wall,uterine penetration and parametrium implantation nor protrusion of placenta into cervix was found between the two groups (all P＞0.05).The MRI signs of uterine penetration and parametrium implantation,uterine recess,protrusion of placenta into cervix yielded a specificity and positive predictive value of 100％,respectively.Conclusion Prenatal MRI has high efficacy in the diagnosis of placenta accrete.Placenta accrete should be highly suspected especially in the presence of uterine penetration and parametrium implantation,uterine recess and protrusion of placenta into the cervix.