To Construct A Predicctive Diagnostic Model Of Placenta Percreta

Objective:（1）To analyze MRI signs of transplacental implantation,establish logistic regression model based on its characteristics,evaluate its diagnostic efficacy,and assist in clinical accurate diagnosis.（2）To evaluate the feasibility of specific signs in the diagnosis of bladder invasion.（3）The value of MRI and ultrasound in the diagnosis of placental implantation was compared.Methods:（1）The MRI images and operation data of 188 patients with placenta accreta confirmed by surgery and pathology from November 2017 to December 2018 were analyzed retrospectively.The average age was（31.9±5.1）years.They were divided into two groups:A and B,of which 143 were used to construct regression model in group A and 45 were used to test the accuracy of the model in group B by external data.Two radiologists with more than 5 years of prenatal diagnosis experience,without knowing the pathological results,scored the placental magnetic resonance signs of each patient with ricketter scale,including placental crypt,different types of placental protrusion,uterine serous vascular sign,placental cavity Inner T2 low signal band and other signs.Single factor analysis was used to screen out the significant signs for the differential diagnosis of penetrating placental implantation,which were further incorporated into the logistic regression model,and the diagnostic efficacy of the model was evaluated by ROC curve.（2）To evaluate the diagnostic value of bladder vascular sign in predicting whether placental implantation involves bladder.（3）The MRI and ultrasound data of 223patients（Group C）who had suspected placental implantation in our hospital from January 2019 to December 2019 were analyzed retrospectively,and the diagnostic efficacy of the two methods for placental implantation was compared.Results:（1）The difference of cesarean section times and intraoperative bleeding between the penetrating placenta and nonpenetrating placenta was statistically significant（2）Chi square test showed that the ten signs of placental crypt,placental apophysis I,placental apophysis II A,placental apophysis II B,serous vascular sign,T2 low signal band,placental signal uneven,placental and uterine junction,placental vascularity were significant to distinguish penetrating placental implantation.（3）Multivariate logistic regression analysis showed that placental crypt,IIA type placental protuberance,serous vascular sign and placental vascular increase were independent risk factors for penetrating placental implantation.The above signs were included in the regression model and the model was:Logit（P）=-7.330+5.604X₁+3.279X₂+4.424X₃+3.019X₄(X₁:the variable value of placental crypt,X_2:the variable value of IIA type of placental eminence,X₃:the variable value of serous vascular sign,X₄:the variable value of placental vascular increase).the joint prediction probability AUC value of diagnosis of penetrating placental implantation is 0.997.（4）Bladder vascular sign has high specificity and positive predictive value for diagnosing bladder invasion,which can be used to evaluate bladder involvement in patients with penetrating placental implantation.（5）here is no significant difference between MRI and ultrasound in the correct diagnosis of placental implantation,but when the placenta is located in the posterior wall,there is a significant difference between MRI and ultrasound in the correct diagnosis of placental implantation.Conclusions:（1）Placental crypt,IIA type placental protuberance,uterine serous vascularization and placental vascularization are of great significance in the differential diagnosis of placental penetration.The combined construction of these signs has practical value in the diagnosis of placental penetration.（2）The bladder vascular sign can be used to assess whether the bladder is involved in patients with penetrating placental implantation.（3）MRI and ultrasound have the same diagnostic effect in placenta accreta,but MRI is better than ultrasound in the diagnosis of placenta accreta with posterior wall.