RESUMEN
Objective To compare the prenatal diagnostic value and image quality of magnetic resonance imaging(MRI)with fast imaging employing steady state acquisition(FIESTA)or single shot fast spin echo(SSFSE)sequence,in order to provide references for sequence selection of prenatal diagnosis.Methods The MRI data of 121 patients with suspected placental invasion were retrospectively analyzed. The ability of FIESTA in displaying MRI signs associated with placental invasion and its image quality were assessed and compared with SSFSE. Based on the records of cesarean section and pathological finding,the sensitivity,specificity,positive predictive values,and negative predictive values of these two sequences were calculated.Results The image quality was significantly higher in FIESTA than in SSFSE(χ =29.74,P=0.000). FIESTA had significantly higher ability to display focal interruptions in the myometrial wall than SSFSE(χ =6.750,P=0.006);in addition,the ability to display abnormal vessel in the placenta(χ =8.471,P=0.020),placental heterogeneity(χ =13.885,P=0.000),hypointense intraplacental bands(χ =4.267,P=0.035)were also significantly higher in SSFSE than in FIESTA,while the efficiency for displaying uterine bulging(χ =0.250,P=0.625),uterine recess(χ =0.167,P=0.687),uterine penetration and parametrium implantation(χ =0.800,P=0.375),and protrusion of the placenta into the cervix(χ =0.081,P=0.776)were not significantly different between these two sequences. Both sequences had a specificity of 100% in displaying uterine penetration and parametrium implantation,uterine recess,and protrusion of the placenta into the cervix. Conclusions FIESTA has better ability in displaying the contour and demarcation of placenta and uterine,whereas SSFSE is more efficient in displaying the changes of intraplacental signals. FIESTA can be used to observe the relationship between the placenta and the surrounding structures and whether the surrounding tissue is implanted,and the changes of placental signals can be observed in SSFSE. The combination of these two sequences can improve the prenatal diagnosis of placenta invasion.