胎儿磁共振成像胎儿磁共振成像MR Imaging of the Fetus超声超声Ultrasound -母体肥胖 -羊水过少 -妊娠中晚期胎头增大 -胎儿颅骨骨化MRIUltrafast MRI -单次激发快速序列 -大FOV -安全性？ MRI仅适用于当产前超声不足以解决临床问题时仅适用于当产前超声不足以解决临床问题时 MRI检查技术1.5T及以下MR机体部相共振线圈序列：单次激发FSE(0.5NEX） FIASTA序列常规轴、冠、矢扫描 胎儿头颅MRI检查胎儿头颅MR检查主要观察 -脑室扩大 -可疑后颅窝异常 -胼胝体发育不良Limperopoulos C, et al. AJR Am J Roentgenol 2008; 190:16371643. Total fetuses MRI abnormal 90 60 (67%)Comparison of antenatal and postnatal MR findings in 39 of 42 live born infantsComplete agreement 23 (59%)Disagreement 16 (41%) Excluded fetal MRI 6 (15%) Revealed additional abnormalities 10 (26%) 枕大池(cisterna magna)正常值211mm侧脑室体部10mm异常表现：Dandy-Walker 畸形，小脑蚓部发育不良，大枕大池，蛛网膜囊肿小脑蚓部的发育1112W，小脑及原始蚓部从第四脑室嘴侧发生1314W，原始顶点可见（第四脑室顶部裂缝）1416W，小脑蚓部原裂出现16W，小脑蚓部向尾侧发育，于顶点处“折叠”覆盖四脑室顶，第四脑室“闭合”1617W，锥前裂、顶前裂等可见1819W，蚓部颅尾方向长度与小脑半球相等 1112W 1314W 16W 18W 17.5w 21w 22w 24w 27wAssessment of Vermian Maturity小脑原裂 primary fissure顶点 fastigial point顶蚓角tengmento-vermian angle，TVA颅尾径 craniocaudal diameter，CCD Normal AbnormalTengmento-vermian angle22week fetusA. axial sonography showed a large cystic posterior fossa with small cerebellar hemispheres.B. the tegmento-vermian angle is increased with the fourth ventricle uncovered . The vermis is very small; there is no primary fissure or fastigial point.C. Diagrammatic representation of DWC.D. the cerebellar hemispheres are small.The ventricular system is dilated, resulting in large temporal horns22week fetusSonography and MRI findings are similar to the previous case except that the cerebellar hemispheres seems larger and vermian tisse can be seen in the midline.Craniocaudal diameterCraniocaudal diameter (perpendicular to fastigial point-declive line)28-week fetusThe craniocaudal diameter of vermis measures 10.9mm (equivalent of 22 weeks). The expected measurement is 14.8mm. The transcerebellar diameter is also small.孕283周，B超提示胎儿脑室扩张14.9mm12.3mm9.8mm上下蚓比小脑蚓部胚胎期呈线性协调发育以顶点为分界上下蚓比例为47和53，不随生长发育变化23-week fetus36-week fetus大枕大池枕大池蛛网膜囊肿29-week fetus5-month孕孕3232周，外院超声提示左脑室扩张、枕大池积水周，外院超声提示左脑室扩张、枕大池积水孕31周，超声提示：可疑侧脑室增宽