The Study Of MRI In Diagnosis Of Placenta Accreta Spectrum And Relationship With Adverse Clinical Outcome

Part 1 The value of MRI in diagnosis and classification of PASObjective MRI has been used increasingly for the prenatal diagnosis of placenta accreta spectrum（PAS）.The objective of the study was to explore the value of MRI signs in diagnosis and classification of PAS.Materials and Methods MRI images of 268 gravid women with high risk for PAS who underwent MRI during the third trimester from 2010 to 2020 were retrospectively analyzed.Univariate analyses and logistic regression analysis were performed to find out independent risk factors of PAS between patients with and without PAS.As independent risk factors for PAS,the MRI signs were scored by simple Logistic scoring model（based on regression coefficient×10）and Additive scoring model（based on odds ratio）and the better score scale was screened according to AUC.The diagnostic value of the scale for PAS classification was evaluated.Results Univariate analyses showed that there were statistically significant differences in all MRI signs except for disruption of low-T2 bladder wall and focal exophytic mass between the PAS group and the non-PAS group（P<0.01）.Logistic regression analysis showed that T2-dark bands,myometrial thinning,abnormal vascularization of the placental bed and placental heterogeneity were independent risk factors for PAS.The simple Logistic scoring scale and the Additive scoring scale could well distinguish PAS from non-PAS,with AUC of 0.8861 and 0.8857,respectively.The simple Logistic scoring scale with a larger AUC was selected and the above 4 MRI signs were assigned 28,20,16 and 13 points,respectively.The cut-off value of 33,36 and 49 could effectively distinguish the non-PAS group and PAS group,the non-deep implantation group and deep implantation group as well as the non-placental percreta group and placental percreta group（AUC: 0.8602-0.8968）,and the sensitivity and specificity were 74.48% and 89.47%,89.58% and 75.00%,and 91.30% and 72.07%,respectively.Conclusion MRI signs had good value in the diagnosis of PAS.The simple Logistic scoring scale simplified the evaluation of PAS invasion depth as well as helped prenatally diagnose and classify PAS to provide a basis for clinical diagnosis and treatment.Part 2 MRI signs combined with clinical characteristics to assess the risk of adverse clinical outcome in gravid women at high risk for PASObjective At present,there is no recognized model for predicting adverse clinical outcome in gravid women at high risk of placenta accreta spectrum（PAS）.The objective of the study was to explore the value of MRI signs combined with clinical characteristics for assessing the risk of adverse clinical outcome in gravid women at high risk for PAS.Materials and Methods MRI images and clinical characteristics of 268 gravid women with high risk for PAS（including 94 patients with adverse clinical outcome and 174 patients without）who underwent MRI during the third trimester from 2010 to 2020 were retrospectively analyzed.Univariate analyses and logistic regression analysis of MRI signs and clinical characteristics were performed to identify independent risk factors for adverse clinical outcome and then logistic regression model combining the independent risk factors were constructed to assess the risk of adverse clinical outcome in gravid women at high risk for PAS.Nomogram was drawn to visualize the model.ROC analysis,calibration curve and decision curve were performed to test the predictive ability.Results Significant differences were found in number of cesarean deliveries,placenta previa and all 11 MRI signs between patients with and without adverse clinical outcome（P<0.01）.The number of cesarean deliveries（X1）,T2-dark bands（X2）,placental bulge（X3）,abnormal vascularization of the placental bed（X4）,placental heterogeneity（X5）and asymmetric thickening of the placenta（X6）were independent risk factors for adverse clinical outcome.The logistic regression model combining the six independent risk factors for assessing adverse clinical outcome was Logistic（P）=-4.435+0.963X1+1.417X2+1.245X3+1.491X4+1.183X5+1.177X6.The AUC of the combined risk model reached 0.9253,which was larger than each of the six independent risk factors（P<0.01）.The diagnostic sensitivity and specificity of the model were 91.49% and 81.03%.The model illustrated good calibration and resulted in high net benefit when the threshold probabilities was 0.05 or above.Conclusion The model combining specific MRI signs and clinical characteristics was benefit to the assessment of the risk of adverse clinical outcome in gravid women at high risk of PAS and improved their prognosis.