MRI在胎盘侵犯术前诊断中的价值

The value of MRI in the prenatal diagnosis of placenta invasion

目的：研究MRI在胎盘侵犯术前诊断中的价值。方法：回顾性分析产前疑似胎盘侵犯的46例孕妇MRI图像,两位阅片者分别记录最佳MRI序列、方位、图像质量、诊断信心、有无侵犯、侵犯深度以及特异性MRI征象;并对两者的结果进行一致性检验。以术后病理或手术记录作为金标准,分别计算MRI诊断胎盘侵犯、侵犯深度以及各个MRI征象的敏感性、特异性、阳性预测值和阴性预测值。结果：两者术前诊断达到中度至高度的一致性（κ值为0.478～0.739）。单次激发闭气序列（SSFSE）及矢状面是最佳的MRI序列和观察方位。MRI诊断胎盘侵犯的敏感度和特异度为79.4%和66.7%;诊断胎盘粘连、植入和穿透的敏感度分别为28.4%,70.6%和33.3%。胎盘与肌层间低信号带缺失在胎盘侵犯中的出现率明显高于无胎盘侵犯（P=0.027）,其胎盘侵犯的阳性预测值为83.95%,敏感度为76.5%。胎盘与肌层间低信号带缺失和T2WI上结节状低信号带同时出现的阳性预测值达到92.3%,但敏感度仅为35.3%。胎盘与肌层间低信号带缺失和子宫下段膨隆同时出现的阳性预测值是100%,但敏感性仅为23.5%。结论：MRI判断有无胎盘侵犯具有较高的敏感性和特异性。判断侵犯深度（粘连、植入和穿透）时敏感性偏低。MRI征象判断胎盘植入具有较高的阳性预测值,但是敏感性偏低。

Objective：To evaluate the preoperative diagnostic value of MRI in placenta invasion.Methods：The MRI features of 46 patients suspected to have placenta invasion were analyzed retrospectively.The optimal sequence and scanning plane of MRI,image quality,presence of placental invasion or not,the depth of invasion and the specificity of MRI features were blindly and independently reviewed by two observers,and the results underwent consistent test.The sensitivity,specificity,positive predictive value（PPV）and negative predictive value（NPV）of the placental invasion,the depth of invasion（accreta/increta/percreta）and the specialized MRI features of placenta invasion were calculated respectively according to the pathological or surgical records.Results：The interobserver agreement of two readers achieved a high level of consistency,and K value was from 0.478 to 0.739.The ideal sequence and observation plane is breath hold single shot fast spin echo sequence（SSFSE）and Sagittal plane.The sensitivity and specificity of MRI for diagnosis of placenta invasion was 79.4%and 66.7%.The sensitivity for diagnosis of the depth of placenta invasion was 28.4%,70.6% and 33.3% for accreta,increta and percreta respectively.The focally interrupted interface between placenta and myometrium was more observed in patients with placenta invasion than patients without placenta invasion（P=0.027）.The PPV and sensitivity of focally interrupted interface between placenta and myometrium was 83.95% and 76.5%,and the combination with the low nodular signal intensity bands on T2 WI improved the PPV to 92.3%,however,the sensitivity was only 35.3%.The PPV of combination of focally interupted interface between placenta and myometrium with bulging of the lower uterus segment improved to 100%;however,the sensitivity was only 23.5%.Conclusion：MRI appears to have good sensitivity and specificity for the diagnosis of placenta invasion,nevertheless it shows low sensitivity for the detection of the depth of placenta invasion（accreta/increta/percreta）.MRI features for the detection of placenta invasion have a high PPV,but low sensitivity.