超声与MRI在胎盘植入诊断中的对比分析

Comparative analysis of ultrasound and MRI in diagnosis of placental accrete

目的评价超声与MRI在胎盘植入(placental accrete,PA)中的诊断价值。方法回顾性收集67例可疑PA并行手术的孕妇,患者先后进行超声和MRI检查。主要观察指标为子宫形态及胎盘附着处肌层形态是否异常,胎盘内/下血管是否增多,胎盘信号/回声是否均质;是否有胎盘陷窝征。检查结果与临床病理对照,采用交叉频数、χ~2或Fisher确切概率法评价两种方法诊断PA的敏感度、特异度、一致性、准确性。结果临床病理证实共有51例PA患者。超声正确诊断PA 40例,MRI检出44例,2种方法诊断PA的敏感度、特异度相似,一致性一般,Youden指数相近。但在亚组分析时,MRI在诊断子宫后壁PA时具有优势,敏感度(87% VS 61%)、Kappa值(0.6 VS 0.2)、Youden指数(0.6 VS 0.4)均大于超声。最常见的影像征象为:胎盘增厚,胎盘附着处子宫肌层变薄、波浪状改变或连续性中断;胎盘内/下血管增多,在超声上见胎盘陷窝征,在核磁共振T_2WI上胎盘信号不均质。结论超声诊断PA的敏感度、特异度、一致性、准确性与MRI类似,但当胎盘位于子宫后壁时,MRI可作为超声的重要补充手段,提高诊断准确性。

Objective To evaluate the value of ultrasonography and MRI in the diagnosis of placental accrete. Methods A retrospective study was performed on 67 pregnant women who were high risk for placental accrete and underwent ultrasonography and MRI before operation. The critical observation indicators as follow：whether the uterine morphology and the placenta adhesion were abnormal,whether there was an increase in the placenta/lower blood vessels,whether the placental signal/echo was homogenous,and Whether there is placental depression sign. Compared with clinical and pathology,the sensitivity,specificity,consistency and accuracy of two methods for diagnosing placenta implantation were evaluated by cross frequency,χ^2 or Fisher exact probability method. Results 51 patients having placental accrete were confirmed by the clinical and pathology. 40 cases were correctly diagnosed by ultrasonography,44 cases were detected by MRI. Sonography sensitivity,specificity,consistency and Youden index was similar with MRI. However,in subgroup analysis,MRI had the advantage in diagnosing posterior placenta implantation,sensitivity（87% VS 61%）,Kappa value（0.6 VS 0.2）,and Youden index（0.6 VS 0.4） were all greater than that of ultrasound. The most common imaging features are： placenta thickening,uterine muscle layer thinning,wavy change or continuous disruption at the placenta attachmen;increasd in the placenta/lower blood vessels,which are seen in the ultrasound-induced placental recess sign,and on the MRI T2WI,the placenta signal is unevenly distributed. Conclusion Sonography sensitivity,specificity,consistency and Youden index was similar with MRI. When the placenta is located in the posterior wall of the uterus,MRI can be used as important supplement of the ultrasonic method,improved the diagnostic accuracy.