Predicting Blood Loss In Suspected Placenta Accreta Spectrum:Evaluated By Graded Or Quantified Magnetic Resonance Imaging Features

Objective To investigate the relationship between graded or quantified magnetic resonance imaging(MRI)features and the amount of haemorrhage in caesarean section for the patients with suspected placenta accreta spectrum(PAS).Methods Patients included in this study have showed one or more suspicious signs of PAS during prenatal ultrasound screening,and also have had one or more clinical high risk factors for PAS.The magnetic resonance(MR)examination was taken after 28 gestational weeks of each patient.The necessary scan sequences included:1.Fast imaging employing steady state acquisition(FIESTA);2.Single-shot fast spin-echo T2-weighted imaging(SSFSE T2WI);3.Liver acquisition with volume acceleration(LAVA).The sequences were obtained in coronal,sagittal and axial planes.The acquired images were uploaded to the picture archiving and communication system(PACS).Two radiologists respectively with 5 years and 8 years experience in MR diagnosis jointly diagnosed,processed and analyzed the MR images of each patient.Two MRI features--myometrial thinning and T2WI dark intraplacental bands(DIB)were selected and measured.Then,the myometrial thickness of each patient was graded and the volume of DIB was calculated for subsequent analysis.Patients were divided into two groups according to estimated blood loss(EBL)and transfusion of red blood cell(RBC)(general blood loss[GBL,EBL<2000ml,and transfusion of RBC<10u];massive blood loss[MBL,EBL>2000ml,or transfusion of RBC>10u]).Statistic analysis of data was conducted by SPSS 23.0 to compare the distribution of the two MRI features between the two groups,and also to compare the correlation of the two features to the EBL and transfusion of RBC.Results Forty-four pregnant women with suspected PAS were enrolled in the study.The age of patients range from 27-40 years,and the average age was 33.25 years.The gestational weeks of each patient at the time of MR examination was between 28-40 weeks.Of 44 patients,33 patients were in the group of GBL and 11 patients were in the group of MBL.Significant difference as regards the grades of myometrial thickness,as well as the volume of DIB,could be found between GBL and MBL groups(p<0.01).Significant negative relation was detected between the grades of myometrial thickness and EBL(p<0.01,Spearman rho=-0.496),as well as transfusion of RBC(p<0.01,Spearman rho=-0.461).Significant positive relation was detected as regards DIB volume to the EBL(p<0.01,Spearman rho=0.535),as well as transfusion of RBC(p<0.01,Spearman rho=0.638).The sensitivity and specificity of the DIB volume in detecting MBL were respectively 81.8%and 81.8%.The area under ROC curve(AUC)was 0.884.Of 44 patients,31 were in the group of PAS,13 were in the group of non-PAS.No significant differences in myometrial grades(P=0.370)and the volume of DIB(P=0.497)were found between PAS and non-PAS patients.Conclusion Myometrial thinning and the volume of DIB are valuable indicators to evaluate the risk of massive bleeding for patients with suspected PAS.