目的 探讨产前胎盘植入MRI表现 及其诊断价值。方法 收集105例临床疑产 前胎盘植入患者相关资料，包括妊娠史 等一般资料、术前ＭＲI和超声所见和诊 断、手术和/或病理结果，以手术和/或病 理结果为参照标准，分析胎盘植入的主要 MRI征象，评估MRI与超声预测胎盘植入的 诊断效能；评价MRI与手术或病理分型诊 断的一致性。结果 105例疑有胎盘植入患 者中，病理证实有胎盘植入的45例，其中 穿透性植入22例、肌层植入13例、胎盘粘 连10例；MR拟诊阳性或可疑阳性74例。 MR评估产前胎盘植入的灵敏度0.98、特异 度0.48、阳性预测值0.55、阴性预测值 0.97；超声产前胎盘植入的灵敏度0.52、 特异度0.86、阳性预测值0.76、阴性预 测值0.73，两者差异有统计学意义，P值 ＜0.05。在产前胎盘植入的MR各种征象 中，子宫肌层与胎盘结构分界不清的有51 例，真阳性者36例，假阳性者15例,准确 率71%；胎盘与膀胱壁分界不清的有3例， 准确率100%；其他征象都相对少见或价值 有限。结论 MRI对产前胎盘植入诊断灵敏 度较超声好，但特异度低于超声。采用 MRI对胎盘植入进行诊断时，可显示多种 相关征象，其中膀胱壁与胎盘结构分界不 清为诊断胎盘植入的最可靠征象。

Objective To investigate the MR imaging findings of placental implantation and its prenatal diagnostic value. Methods Data of 105 patients with suspicion of placental implantation who had undergone MR and color Doppler ultrasound (US) evaluation in the second and third trimester gestation were collected retrospectively, including MRI findings and color Doppler ultrasonography of the placental implantation, the prenatal diagnosis, surgical evidence, pathological diagnosis, and so on. Taking surgical evidence or histopathology as reference, the sensitivity, specificity, positive predictive value, negative predictive value and accuracy of MRI and US for the evaluation of placental implantation were determined. Results Of the 105 patients with suspicion of placenta implantation, 45 cases were consistent with pathology, including 22 cases of penetrating implantation, 13 cases of myometrium placenta implantation, and 10 cases of placenta adhesion; and 74 patients were assumed placenta accrata or suspected placenta accrata based on MRI. The sensitivity, specificity, positive predictive value, and negative predictive value of MRI and US for the evaluation of placenta implantation were 0.98 and 0.52, 0.48 and 0.86, 0.55 and 0.76, and 0.97 and 0.73, respectively(P<0.05). On MRI imaging, 51 patients showed lose of or ambiguous and blurry placental myometrial interface, 36 of them had placenta implantation, 15 of them did not have placenta implantation, and the accuracy was 71%. 3 patients with lose of the placental urinary bladder interface showing on the contrast-enhanced MRI were confirmed placenta implantation, the accuracy was 100%; the other abnormal findings on MRI were relatively rare, and they had limited value for the evaluation of placenta implantation. Conclusion Compared with color Doppler ultrasonography for the evaluation of placenta implantation, MRI has higher sensitivity and lower specificity. The lose of the placental urinary bladder interface on the contrastenhanced MRI is a reliable characteristic for the diagnosis of placenta implantation.