The Study Of Diagnosic Value Of Prenatal MR Imaging Examination In Placental Invasion And Different Types

objective: To investigate the value of magnetic resonance imaging(MRI)for the diagnosis of prenatal placental invasion and different invasive types.To summarize the main MRI imaging features of the placental invasion,To explore the efficiency of each MRI sign in predicting placental invasion and the difference of the displaying rates in the three types.Methods : 129 patients who were suspected placental invasion by ultrasound or clinic underwent MRI examination were searched in the PACS from January 2014 ~ December 2016,62 cases were included according to the inclusion and exclusion criterias finally.Collecting the general clinical data of them and dividing them into placental invasion group and without placental invasion group according to the "gold standard" of clinical or(and)pathological diagnosis results.Two radiologists who blinded to the final diagnosis results evaluated the MRI imaging findings of each patient and made the image diagnosis.Evaluation of the consistency between MRI and "gold standard" in the diagnosis of placental invasion by Kappa test.Accuracy,sensitivity,specificity,positive and negative predictive values,Youden index of MRI for the diagnosis of prenatal placental invasion and different types were calculated.To calculate the displaying rates of MRI findings in the two groups of placental invasion and non-invasion and the displaying rates in three different types.Chi-square or Fisher's exact test were used for analysis the correlation between MRI findings and placental invasion or between MRI findings and the three different types.To calculate the efficiency of each MRI finding in the diagnosis for placental invasion.The thickness of the placenta in each patient was measured and the difference of the thickness between the two groups of placental invasive and non-invasive was compared.To measure width of the widest vessels in the placenta and analyze the correlation between the width of the vessels and grading diagnosis using the Spearman rank correlation.Results:(1)42 patients were diagnosed to have placental invasion and 20 patients without by the "gold standard".Among the placental invasion group,17 of them were placenta accreta,20 with placenta increta and 5 with placenta percreta.(2)The Kappa value was 0.72 between MRI and "gold standard" in the diagnosis of placental invasion.The accuracy,sensitivity,specificity,positive and negative predictive values,Youden index of MRI for the diagnosis of prenatal placental invasion was 87.10%,85.71%,90.00%,94.74%,75.00%,0.76 respectively.The Youden index was lowest for the diagnosis of placenta accreta with 0.34 and highest for placenta percreta with 1.(3)The following five MRI findings were statistically significant difference for the diagnosis of invasive placenta: heterogeneous placenta,blurring or defect of interface between myometrium and placenta,abnormal uterine and(or)placenta bulging,disorganised abnormal intraplacental vascularity,dark intraplacental bands on T2 W.(4)Blurring or defect of interface between myometrium and placenta was the most accurate and sensitive criteria with 82.28% accuracy and 83.33% sensitivity for the diagnosis of placental invasive.Abnormal uterine and(or)placenta bulging,focal disruption of uterine serosa,invaded of bladder or pelvic other tissues and organs,hemorrhage intraplacental were the most specific criteria with 100.00% specificity of all for the diagnosis of invasive placenta.(5)The displaying rates of thinning and focal disruption of myometrium,Abnormal uterine and(or)placenta bulging,disorganised abnormal intraplacental vascularity,focal disruption of uterine serosa,invaded of bladder or pelvic other tissues and organs were statistically difference amoung the three different types of placental invasive.(6)The mean thickness of the placenta was statistically significant difference(P= 0.012)between the groups of placental invasion and non-invasion.(7)The width of the vessels in the placenta were statistically significant difference among the three different types of placental invasion.the width of the vessels was correlation with the invading depth.(P = 0.033,rs = 0.446).Conclusions:(1)There is good consistence between MRI results and clinical or(and)pathological diagnosis results in the diagnosis of placental invasive(Kappa=0.72)and the overall diagnostic performance is substantial,MRI can be an important method for prenatal diagnosis of placental invasive.(2)MRI plays a significant role in the classification of placenta invasive to a certain degree,the accuracy of diagnosis for placenta percreta is highest and the placenta accreta is easily missed.(3)The five MRI findings of heterogeneous placenta,blurring or defect of interface between myometrium and placenta,abnormal uterine and(or)placenta bulging,disorganized abnormal intraplacental vascularity,dark intraplacental bands on T2 W can be the diagnostic criteria for the diagnosis of invasive placenta.Blurring or defect of interface between myometrium and placenta is the most accurate and sensitive criteria.(4)Focal disruption of uterine serosa,invaded of bladder or pelvic other tissues and organs are the most specific criteria in the diagnosis for placenta percreta.(5)The width of thickened vessel intraplacental is associated with the classification of placental invasive,the wider the blood vessels thicken,the deeper the placenta invade.