Clinical Application Value Of MRI Imaging Technique In Diagnosis Of Placenta Accreta Spectrum

First part Purpose The aim of this study was to compare the overall diagnostic accuracy of MRI and ultrasound(US)in detecting the placenta accreta spectrum(PAS).Methods In this systematic review and meta-analysis,we independently searched 9 databases(Pubmed,MEDLINE,Embase,Elsevier,The Cochrane Library,SinoMed,WANFANG DATA,China National Knowledge Infrastructure,VIP),and ClinicalTrials.gov for studies published between Jan 1,1998,and Sep 1,2018,for case-control trials comparing the use of MRI and US in diagnostic PAS.Studies were excluded if they were review articles,editorials,letters,or case reports.We assessed the quality of the studies using the quality assessment of diagnostic accuracy studies(QUADAS-2),and contacted authors for the provision of additional data if needed.We screened studies and extracted data from published reports independently.The primary outcomes were measures of sensitivity,specificity,DOR,positive likelihood ratio(LR+),negative likelihood ratio(LR-)and accurary,summary receiver operating characteristic curves and areas under the curve(AUCs)which were assessed by random-effects and fixed-effects meta-analysis.Results 58 studies(5569 pregnancies)were included.The MRI diagnosed included 1442 cases of PAS,US diagnosed PAS totaled 1513 cases.The sensitivity,specificity,DOR,LR+,LR-and accurary was 0.83(95%CI: 0.81-0.85),0.80(95%CI: 0.78-0.82);0.89(95%CI: 0.88-0.90),0.92(95%CI: 0.91-0.93);31.03(95%CI: 20.85-46.18),31.46(95%CI: 21.55-45.93);5.33(95%CI: 4.07-6.97),5.98(95%CI: 4.42-8.10);0.21(95%CI: 0.18-0.26),0.25(95%CI: 0.21-0.30);0.87(95%CI: 0.85-0.88),0.88(95%CI: 0.87-0.89)respectively.And the AUC under the SROC curve was 0.8711,0.8965.Conclusion The Meta-analysis showed that the diagnostic value of MRI for PAS was no statistically significant compared with US.Despite the high sensitivity and specificity of both MRI and US diagnostic PAS,most small sample studies use MRI imaging as an adjunct to ultrasound.Multi-center study is recommended to further improve the accuracy of MRI diagnosis of PAS,and MRI as a screening method for PAS in high-risk pregnant women.Second partPurpose Analyze the consistency of common signs recognition of different radiologists on magnetic resonance(MRI)diagnosis of placenta accreta spectrum(PAS),and improve the stability of various signs in clinical work.Methods Two experienced radiologists of the same working age,which evaluate various MRI signs of suspected PAS patients who were delivered to Zhongda Hospital affiliated to Southeast University from October 1,2014 to October 31,2018,and confirmed the presence of PAS and degree.Results There were some differences in the diagnosis of placenta implantation between the two observers,but the overall diagnosis was not statistically significant(P>0.05);kappa results showed that the K values for normal placenta and placenta accreta were 0.419 and 0.422,respectively(P<0.05);the K values for placental increta and percreta were 0.667 and 0.735,respectively(P < 0.05).There were some differences between the two observers in the evaluation of common MRI signs of suspected PAS,but the overall evaluation was not statistically significant(P>0.05);Kappa test results showed that the K value of placental recess accompanied by a T2 dark band was 0.840(P<0.05),and intra-placental T2 dark band(s)was 0.695(P<0.05).The K value of the heterogeneous placental signal intensity was 0.675(P<0.05);focal interruption of the myometrium,s K value was 0.643(P<0.05);the evaluation of placental bulge(including type I and type II,the latter is divided into IIa,IIb)was 0.612(P< 0.05).Conclusion MRI signs of placenta acreta spectrum subjectively judged the differences between individuals,including " cervical varicosities,uterine bulging,tenting of the bladder,placentale-uterine myometrial interface disappeared,uterine serosa vascular enlargement,intraplacental abnormal vascularity.The evaluation of the myometrial thinning is poor,and the evaluation of intra-placental T2 dark band(s),the heterogeneous placental signal intensity,focal interruption of the myometrium,and placental bulge(type I,IIa,IIb)are more consistent good;the judgment of "placental recession with T2 dark band" is the best.Third partPurpose To study the accuracy of prenatal magnetic resonance imaging in the diagnosis of various types of placenta accreta spectrum.Methods A retrospective collection of 84 pregnant women from January 1,2016 to January 31,2019,who underwent cesarean section at Zhongda Hospital affiliated to Southeast University and underwent prenatal magnetic resonance examination.Results Of the 84 pregnant women who underwent cesarean section,48 cases were confirmed by surgery and pathology as PAS patients,30 cases were placenta accreta,10 cases were increta,and 8 were percreta.MRI accurately diagnosed placental accreta in 13 cases(43.3%,X2=1.714,P =0.189),placenta increta in 6 cases(60%,X2=2.25,P=0.625),placental percreta in 8 cases(100%).The overall sensitivity and specificity of MRI for diagnosis of all types of PAS were 56.3%(95% CI: 41.7-70.8)and 77.8%(95%CI: 63.5-92.0),positive and negative predictive values were 77.1%(95% CI: 62.5-91.8)and 57.1%(95% CI: 42.8-71.5),respectively.Accuracy was 65.5%(95% CI: 55.1-75.9).The sensitivity,specificity,positive predictive value,negative predictive value and accuracy of MRI in diagnosis of accreta and increta were 48.1%(95 % CI: 28.0-68.3)and 66.7%(95% CI: 28.2-105.1),80.0%(95% CI: 66.1-93.9)and 96.6%(95% CI: 89.5-103.6),65.0%(95% CI: 42.1-87.9)and 85.7%(95% CI: 50.8-120.7),66.7%(95% CI: 51.8-81.5)and 90.3%(95% CI: 79.3-101.3),66.1%(95% CI: 54.0-78.2)and 89.5%(95% CI: 79.3-99.7).The accuracy of MRI diagnosis of placenta percreta was 100.0%.Conclusion The accuracy of MRI in the diagnosis of placental accreta is poor,while the accuracy of diagnosis placental increta and percreta are better.However,Above findings come mainly from pregnant women with suspicious PAS in which MRI was performed as a secondary imaging tool in women already screened for PAS on ultrasound and might not reflect its actual diagnostic performance in detecting the various types of PAS.