15～40周胎儿标本脊髓腰骶膨大发育的磁共振研究

目的 研究胎儿标本脊髓腰骶膨大（LSE）面积随胎龄变化的规律及MR表现.方法 收集胎龄15～40周的胎儿标本52例,以L2椎体为中心,行T12～ S1脊椎横轴位、矢状位和冠状位3.0T MRI T2WI扫描,观察脊髓LSE最大横断层面的前后径、左右径、面积及相应水平椎管面积,计算脊髓LSE最大横断层面的面积与相应水平椎管面积的比值,对上述测量结果和胎龄间的关系做回归分析.结果 在52例胎儿标本中,MRI T2WI横断面上脊髓清晰显示45例（86.54％）,显示不清7例（13.46％）;于胎龄15周在脊髓横断面显示脊髓信号和LSE信号,27周以前脊髓LSE呈“两环结构”,33周以后脊髓的双环样信号不明显.脊髓LSE最大横断层面的前后径、左右径及面积随胎龄的增加呈线性增长（P值均＜0.01）,脊髓LSE最大横断层面的面积与相应水平椎管面积的比值随胎龄的增加逐渐减小（P值均＜0.01）.结论 MR可清晰显示胎儿脊髓LSE在不同胎龄的发育表现及其与胎龄的变化规律.

Postmortem MRI of normal fetal lumbosacral enlargement

Objective To study the normal development of the fetal lumbosacral enlargement （LSE） at different gestational ages with postmortem MRI.Methods Postmortem MRI was performed on 52 fetuses ranging from 15 to 40 gestational weeks.T2-weighted MRI of the lumbar spine was performed in the coronal,sagittal and axial plane.The anteroposterior diameter,the area of LSE,the area of vertebral canal and the ratio of LSE to the overall size of the vertebral canal were measured.The relationship between the measurement results and gestational weeks were analyzed by linear regression.Results Fifty-two cases of fetal specimen were observed on T2-weighted imaging （T2WI） of magnetic resonance imaging （MRI）.Forty-five spinal cords （86.54%） could be showed clearly and 7 spinal cords （13.46%） couldn＆#39;t be showed clearly,the spinal cord and LSE signal could be showed on MRI T2WI at 15 gestational weeks.The LSE appeared double circle signs on T2WI before 27 gestational weeks.The double circle signs of LSE couldn＇t be showed clearly after 33 gestational weeks.Anteroposterior diameter,transverse diameter and the area of the LSE increased linearly with gestational age （all P values 〈 0.01）.The ratio of LSE to the overall size of the vertebral canal increased with gestational age （all P values 〈 0.01）.Conclusions The normal growth and signal-intensity characteristics of the LSE can be well described by postmortem MR imaging.