Application Of MRI In The Diagnosis And Differential Diagnosis Of Fetal Posterior Fossa Cistern Malformation In Midsagittal Position

Objective To observe the MRI morphology of posterior fossa cistern based on midsagittal MRI,establish three characteristic measurement methods to study the relationship between the measurement values of normal fetus and gestational age,and analyze and compare the differences between common posterior fossa cistern malformations and the measured normal values.Methods 132 cases of normal fetuses and 48 cases of abnormal fetuses underwent prenatal ultrasound scan and MRI scan of fetal brain within 72 hours were analyzed retrospectively.The outcomes were confirmed after labor induction or delivery.The MRI morphology of posterior fossa cistern was observed in midsagittal view,and the superior posterior fossa angle(SPFA),tegmento-vermian angle(TVA)and posterior fossa perimeter(PFP)of the fetus were measured.Spearman correlation analysis was used to discuss the correlation between the measured values and gestational age,and the difference between abnormal fetal group and normal fetal group was analyzed.Results1.Clinical data 132 normal fetuses and 48 abnormal fetuses were included in this study,including 25 cases of MCM(52%),9 cases of DWM(19%),8 cases of IVH and(17%)and 6 cases of BPC6(12%),respectively.MCM had the highest incidence among abnormal fetuses included in this study.All 180 pregnant women ranged in age from 18 to 43 years old,with an average age of 28.2±4.4 years old.The gestational age of the fetus ranged from 23 to 37 weeks,with an average gestational age of 29.5 ± 3.5 weeks.2..MRI results of fetal brain median sagittal in 132 cases of normal groupThere was no correlation between TVA and SPFA with gestational age(r =0.097,r = 0.042,P > 0.05).The mean Angle of TVA was 3.63° ± 0.98°,and the mean Angle of SPFA was 94.51° ± 2.60°.PFP was significantly positively correlated with gestational age(r = 0.949,P < 0.05).Linear regression analysis showed that the linear regression equation between PFP(Y)and gestational age(X)was Y=-4.11+ 4.04 X.3.The results of MRI in median sagittal of fetal brain in 48 cases of abnormal groupscores of SPFA in DWM and IVH were greater than 6 standard deviations,and scores of 76%PFP were greater than 6 standard deviations.Z-scores of94%SPFA in MCM and BPC were less than 6 standard deviations,and Z-scores of97%PFP were less than 6 standard deviations.TVA of DWM were all greater than29°,and the maximum Angle of 1 case was 43.5°.TVA of IVH was between20°-29° and that of BPC was between 14°-19°,There was no significant difference in TVA between MCM and normal group.Conclusions1.There was no correlation between TVA and SPFA and gestational age.The average Angle of TVA was 3.63 ° ± 0.98 °,and the average Angle of SPFA was94.51°±2.60°.The linear regression equation between PFP(Y)and gestational age(X)is Y=-4.11+4.04 X.2.The Z scores of SPFA and PFP of DWM and IVH were more than 6standard deviations higher than those of the normal group,indicating that the posterior fossa was obviously larger than that of the normal group.SPFA and PFP could determine whether the size of the posterior fossa was enlarged and whether the sinusitis was abnormally elevated.3.TVA greater than 29° suggests DWM,TVA between 20°-29° suggests IVH,and TVA between 14°-19° suggests BPC.