Cesarean Scar Pregnancy:Comparative Study Of Ultrasonography And MRI In Scar Thickness Measurement

Preoperative medical imaging evaluation of cesarean scar pregnancy(CSP)scar thickness affects the clinical decision making.Ultrasonography(US)is the first line diagnostic tool for CSP.Because of the relatively low resolution,scar thickness evaluated by US can only be obtained indirectly by measuring the distance between anterior edge of gestational sac and posterior wall of bladder.It is a consensus that magnetic resonance imaging(MRI)is superior to US in the resolution of soft tissue.However,due to its high cost and time-consuming,most authors do not recommend MRI as a routine method for CSP diagnosis,and believe that US is a reliable method to ensure correct evaluation.MRI is only used as an auxiliary means when the US diagnosis is uncertain.The high trust of US in diagnosing CSP in the past has led to the common view that US is also reliable in evaluating CSP scar thickness.In recent years,the comparative study of US and MRI in measuring CSP scar thickness has been controversial,but it has not been confirmed due to the lack of relevant research and reliable gold standard.In order to select more accurate examination methods to guide clinical decision-making,we conducted a comparative study on the accuracy of US and MRI in measuring CSP scar thickness from the following three parts.PART 1 Cesarean Scar Pregnancy:Comparative Reliability of Ultrasonography and MRI in Measuring Scar ThicknessObjective To evaluate the agreements of Ultrasonography(US)and Magneti Resonance Imaging(MRI)in measuring CSP scar thickness.Methods In this prospective study,59 consecutive CSP patients suspected by US and confirmed by postoperative pathology were included.Additional MRI FRFSE T2WI PROSPER and T2W+FS PROSPER scans were performed on the oblique sagittal plane of CSP.According to the MRI signal changes of the gap between the thinnest scar and posterior wall of bladder,the participants were divided into low signal,fat signal and water signal group.The thinnest scar thickness was measured by transvaginal ultrasound(TVS),MRI T2WI and T2WI+FS sagittal imaging perpendicular to the surface of CSP scar.Results 59 patients with CSP,aged 25-42 years(33.9±4.4 years)with previous cesarean section once in 29 cases(49.1%),twice in 28 cases(47.4%),and three times in 2 cases(3.5%),menopause for 4-12(7.5±2.1)weeks,0.5-8(3.20±2.21)years from the previous CSP,and 0.3-2(2.5±1.1)days of interval between US and MRI scans,were enrolled in the study.For the CSP scar thickness measurement,the agreements were excellent(ICC=0.925)for T2WI,good(ICC=0.799)for T2WI+FS,and general(ICC=0.709)for US.The agreements were good(ICC=0.823)between T2WI and T2WI+FS,general(ICC=0.627 and 0.667)between US and T2WI and T2WI+FS,respectively.In 11cases of low signal group,the agreements of scar thickness measured by T2WI(ICC=0.829)and T2WI+FS(ICC=0.836)were good,and of US was general(ICC=0.701).The agreements were excellent(ICC=0.997)between T2WI and T2WI+FS,and poor between US and T2WI(ICC=0.270)and T2WI+FS(ICC=0.285),respectively.In 22 cases of fat signal group,the agreements of scar thickness measured by T2WI were excellent(ICC=0.935),general by US(ICC=0.703)and T2WI+FS(ICC=0.702),good between T2WI and T2WI+FS(ICC=0.782),and general between US and T2WI(ICC=0.646)and T2WI+FS(ICC=0.691),respectively.In the MRI water signal group,the agreements of T2WI were excellent(ICC=0.943),of T2WI+FS were good(ICC=0.899),of US were general(ICC=0.708).Agreements between T2WI and T2WI+FS were excellent(ICC=0.955),and between US and T2WI(ICC=0.836)and T2WI+FS were good(ICC=0.870),respectively.Conclusion MRI,especially T2WI,is more reliable than US in detecting CSP scar thickness.The reliability of T2WI+FS in patients with fat signal uterine-bladder space in MRI decreased to the same lever as US.US showed stable general reliability in all patients.PART 2 Cesarean Scar Pregnancy:Comparative Accuracy of US and MRI in Measuring Scar ThicknessObjective To evaluate the accuracy of US and MRI in the measurement of CSP scar thickness,and the possibility of in vitro CSP scar thicknes measurement under microscope as reference standard of CSP scar thickness.Methods Patients of US suspected CSP with preoperative uterine MRI,and confirmed pathologicly were prospectively included,and divided into low signal,fat signal and water signal group according to the MRI signal of CSP scar-bladder space.Thickness of the thinnest scar was measured by TVS,T2WI and T2WI+FS.The distance from the leading edge of gestational sac to the posterior wall of bladder was measured by T2WI(Named"T2WI-GTB").The degree of adhesion between uterus and bladder in the operation group was evaluated,and the thickness of the thinnest scar was measured in vitro under microscope.Compatibility analysis of variance was used to analyze the relationship between the measurements.The distribution consistency of adhesion degree in uterine-bladder space in different signal groups was analyze.Results 59 patients with CSP were finally enrolled,including 40 cases in the operation group and 19 cases in the curettage group.During the operation group,100%(n=40/40)of the patients had adhesion between uterus and bladder,including 24 cases of membranous adhesion,2 cases of muscular adhesion and 14 cases of dense adhesion.The adhesion degree in the MRI low signal uterine-bladder space was higher than that in other groups.Under the microscope,smooth muscle cells were commonly found in the thicker area,while fibrous connective tissue was more commonly found in the thinnest area.The mean values of CSP scar thickness measured by US,T2WI,T2WI+FS and T2WI-GTB were 3.12±1.28 mm,1.63±0.83 mm,1.92±0.86 mm and 3.04±1.16mm,respectively.There was no significant difference between US and T2WI-GTB(P>0.05),which were higher than that of T2WI and T2WI+FS.The value of T2WI+FS was higher than that of T2WI(P>0.05).In MRI fat signal uterine-bladder space cases,the measured values of T2WI+FS were higher than that of T2WI(P<0.001).In cases with MRI low signal or water signal uterine bladder space,there was no significant difference between T2WI and T2WI+FS(P>0.05).Regardless of the signal changes in the uterine-bladder space,there was no significant difference between US and T2WI-GTB(P>0.05),which were higher than T2WI and T2WI+FS(P<0.001),respectively.Compared with other cases(water sample or/and fat signal),there was no significant difference in the measured values of US,T2WI,T2WI+FS and T2WI-GTB(P>0.05)in the cases of MRI low signal in uterine-bladder space.The CSP scar thickness measured by US was greater than that measured in vitro under microscope.There was no significant difference between T2WI,T2WI+FS and the in vitro thickness measurement under microscope(P>0.05).Conclusion There were significant differences in the accuracy of US,T2WI and T2WI+FS in measuring the thinnest CSP scar thickness.T2WI measurement is the most accurate,and T2WI+FS is second due to the decreased measurement accuracy of cases with fat signal in the uterine-bladder space.However,US measurement had the error of systematicly including the uterine-bladder space into scar thickness measurement,resulting in higher value than that of MRI.The low MRI signal intensity of uterine-bladder space indicates dense adhesion between CSP scar and bladder.The thickness of thinnest CSP scar changes little in vivo and in vitro,indicating that the measurement of in vitro may be a reference standard for the measurement of CSP scar thickness.PART 3 Cesarean Scar Pregnancy:Value of Measuring Scar Thickness by Ultrasound and Magnetic Resonance T2WI in Assessing Treatment RiskObjective To explore the value of US and MRI measurement of CSP scar thickness in assessing treatment risk,and the feasibility of using US measurement results to predict MRI and microscopic measurement of scar thickness of specimens.Methods The data of scar thickness measured by US and T2WI in 59 CSP patients were analyzed prospectively.According to the standard of intraoperative bleeding,the curettage group CSP patients(n=18)were divided into bleeding and non-bleeding group.The difference of scar thickness measured by US and T2WI between the two groups was analyzed.The area under curve(AUC)was calculated by receiver operating characteristic(ROC)to evaluate the value of scar thickness measured by US and T2WI in the diagnosis of bleeding during uterine curettage and the possible diagnostic threshold.Simple linear regression analysis was used to evaluate the feasibility of US measurement of CSP scar thickness to predict MRI results,and the feasibility of US and MRI results to predict the thickness measurement of scar in vitro.Results The CSP scar thickness measured by T2WI was significantly higher in non-bleeding group than that in bleeding group(P<0.001).There was no significant difference between the two groups(P=0.324)while measured by US.The AUC of CSP scar thickness measured by US for the diagnosis of bleeding during uterine curettage was 0.733(P=0.214).While measured by T2WI,the AUC of CSP scar thickness for the diagnosis of bleeding during uterine curettage was 1.00(P=0.008)with a threshold of 1.15mm,and the sensitivity and specificity of 100%,respectively.Simple linear regression analysis was carried out with the common logarithm transformation of CSP scar thickness measured by T2WI as the dependent variable and by US as the independent variable,and the linear regression equation was Y=0.093X-0.125,with R2=0.352.Simple linear regression analysis was carried out with the common logarithm of the CSP scar thickness measured in vitro as the dependent variable and by US as the independent variable,and the linear regression equation was Y=1.08X-0.74,with R2=0.327.Simple linear regression analysis was carried out with the common logarithm of the CSP scar thickness measured in vitro as the dependent variable and by T2WI as the independent variable,and the linear regression equation was Y=0.265X-0.251,with R~2=0.65.Conclusion US measurement of scar thickness has limited value in the diagnosis of bleeding during uterine curettage,while T2WI measurement has high diagnostic value.When the CSP scar thickness measured by T2WI is lower than 1.15mm,the sensitivity and specificity of predicting bleeding during curettage are 100%,respectively.Using CSP scar thickness measured by US to predict T2WI results or the in vitro scar thickness has little clinical value.The clinical application of T2WI thickness measurement to predict scar thickness in vitro has improved,but it is also limited.After the preferred US examination suspected or confirmed CSP,we strongly recommend further MRI T2WI measurement of scar thickness to accurately guide clinical treatment decisions and reduce complications and surgical invasion.