妊娠期胎盘植入MRI的诊断评价及植入范围分级的临床意义

Diagnostic value of MRI on placental invasion and clinical value of the topography classification

目的:分析与妊娠期胎盘植入相关的磁共振特征,探讨植入范围MR分级对临床治疗的指导意义。方法:回顾性分析2009年12月—2014年5月期间在本院超声产检发现前置胎盘、怀疑胎盘植入并进一步行MRI检查的资料,以手术和病理结果为标准,对胎盘植入的MRI征象,包括子宫肌层变薄、胎盘-肌层交界面消失、胎盘内部带状T2WI低信号影、子宫轮廓外突以及最终诊断的灵敏度、特异度、阳性预测率以及阴性预测率。根据MRI横断图上最大植入面的范围,对确诊病例进行MR分级,植入面≤50%的为A级,植入面>50%的为B级,出现浆膜外侵犯的为C级,通过χ2检验比较不同分级之间保守治疗成功率的差异。结果:69例怀疑胎盘植入的病例中有46例被最后确诊,其中43例被MRI正确诊断(灵敏度93.48%),21例被正确排除(特异度91.30%)。MRI征象中以胎盘-肌层交界面消失的灵敏度及阴性预测率最高(95.56%,90.0%),子宫肌层变薄次之。T2WI胎盘内低信号带的阳性预测率较高(90.01%),子宫轮廓外突的特异度及阳性预测率最高(100%)。植入范围MR分级保守治疗的成功率分别为100%(A级)、23.08%(B级)和12.5%(C级),统计学分析有明显差异(P<0.05)。结论:MRI在胎盘植入的诊断方面有较大优势,以胎盘-肌层交界面消失为最佳诊断依据。根据植入范围的MR分级方法对治疗手段的选择有一定的指导意义。

Objective： To analyze MRI features of placental invasion and evaluate the clinical value of MR topography classification. Method： Records from December 2009 to May 2014 were reviewed to identify the accuracy of MRI in the di- agnosis of placental invasion in the patients with a diagnosis of placenta previa and suspected placental invasion by ultra- sound. Sensitivity, specificity, PPV and NPV were calculated on each MRI feature of placental invasion including myometrial attenuation, loss of placental-myometrial, interface, T2WI dark bands and outward protruding of the uterus. All final diagnosis was based on surgical and pathological findings. MR topography classification was carried out on confirmed cases according to the topography of placental invasion. Over 50%, no more than 50% of uterine axial circumference and parametrial invasion were categorized as invasion of category A, B and C. Success rates of conservative treatment were compared by X^2 test be- tween each category. Result： Of the 69 suspected cases, 46 had confirmed placenta invasion. MRI accurately predicted pla- centa invasion in 43 cases（sensitivity 93.48%） and 21 cases were correctly ruled out（specificity 91.30%）. Loss of placental-my- ometrial interface was of the highest sensitivity and NPV （95.56%, 90.0%）, followed by myometrial attenuation. T2WI dark bands was of high PPV（90.01%）, and outward protruding of the uterus was of the highest specificity and PPV（100%）. Success rates of conservative treatment were 100%（category A）, 23.08%（category B） and 12.5%（category C） with statistical difference（P〈 0.05）. Conclusion： Diagnostic accuracy of MRI is high in evaluating placental invasion. Loss of placental-myometrial interface is the prime feature in assessment. MR topography classification helps to determine conservative treatment.