MRI正中矢状位对胎儿后颅窝池的定量分析

Quantitative Analysis of Fetal Posterior Fossa Cistern in MRI Mid Sagittal Position

目的基于MRI正中矢状位建立三个特征性测量方法,研究正常胎儿各测量值与孕龄的关系并分析对比常见后颅窝池畸形与所测正常值的差异。方法回顾性分析行产前超声检查并在72小时内行胎儿颅脑MRI检查的92名正常胎儿及36例异常胎儿(单纯后颅窝池增宽21例、经典型Dandy-Walker畸形7例、变异型Dandy-Walker畸形5例及Blake’ s囊肿3例),随访至引产或分娩后明确结局。在胎儿正中矢状位测量胎儿上后颅窝角(SPFA)、被盖-小脑蚓角(TVA)、后颅窝周长(PFP),采用Spearman相关分析分析各测量值与孕龄的相关性,并分析异常胎儿与正常值的差异。结果 PFP与孕龄呈明显正相关(R^(2)=0.952,P<0.05),SPFA及TVA与孕龄均不相关(R^(2)=0.055、0.074,P>0.05)。异常组中经典型Dandy-Walker畸形与变异型Dandy-Walker畸形SPFA的Z分数均大于6个以上标准差,73%PFP的Z分数大于6个以上标准差;异常组中单纯后颅窝池增宽与Blake’ s囊肿83%SPFA的Z分数小于6个标准差,79%PFP的Z分数小于6个标准差;经典型Dandy-Walker畸形TVA均>29°,变异型Dandy-Walker畸形TVA介于20°~29°,Blake’ s囊肿TVA介于14°~19°,单纯后颅窝池增宽TVA与正常组未见明显差异。结论 SPFA及PFP是一种基于MRI建立的测量方法,可以确定孕中晚期的后颅窝池预期大小,SPFA、PFP及TVA有助于判断分析常见后颅窝池囊性畸形的诊断及鉴别诊断。

Objective To establish three special measurement methods based on the mid sagittal position of MRI to study the relationship between the measurements of normal fetuses and gestational age, and to analyze and compare the differences between the common posterior fossa malformations and the measured normal values. Methods 92 normal fetuses and 36 abnormal fetuses(21 cases of mega cistern magna, 7 cases of classic Dandy-Walker malformation, 5 cases of Dandy-Walker Variant and 3 cases of Blake ’s cyst) who were examined by prenatal ultrasound and MRI within 72 hours were analyzed retrospectively. Follow up to labor induction or definite outcome after delivery. The SPFA, TVA and PFP were measured in the midsagittal position of the fetus, The correlation between the measured values and gestational age was analyzed by Spearman correlation analysis, and analyzed the difference between abnormal fetus and normal value. Results PFP was positively correlated with gestational age(R^(2) = 0.952, P< 0.05). SPFA and TVA were not correlated with gestational age(R^(2) = 0.055, R^(2) = 0.074, P> 0.05). The z-scores of SPFA of classic Dandy Walker malformation and Dandy Walker variant in the abnormal group were more than 6 standard deviations. The z-scores of 73% PFP were more than 6 standard deviations. In the abnormal group, the z-scores of 83% SPFA and 79% PFP of mega cistern magna and Blake ’s cyst were less than 6 standard deviations.The TVA of classic Dandy Walker malformation was more than29°, the TVA of Dandy Walker variant was between20°-29°. The TVA of Blake’s cyst was between 14°-19°. There was no significant difference between the TVA of mega cistern magna and the normal group. Conclusion SPFA and PFP are measurement methods which are based on MRI,which can determine the expected size in the middle and late pregnancy.SPFA,PFPand TVA are helpful for the diagnosis and differential diagnosis of common posterior fossa cystic malformations.