妊娠中期胎儿海马结构发育的7.0T MRI研究

目的:探讨妊娠中三个月内海马结构发育的形态变化以及其折叠角的变化,分析其发育规律.方法:收集胎儿标本51例,孕龄为14～22周,经超声筛选,排除神经系统异常.用德国产BRUKER 7.0T MR扫描,在二维图像上利用eFilm软件进行形态变化观察.定义海马折叠角(HIA)为海马角外缘和海马下托内上缘的连线与通过中线结构的直线的夹角,并在经过脑桥的冠状面上对此角进行测量.结果:13～14周时,海马结构几乎没有折叠,其皮层有3层结构,即室周层、中间带和皮质板;15～17周时,齿状回和海马角开始向颞叶内部折叠,海马结构典型特征是表现出明显的板层结构,CA2和CA3区的皮层逐渐变窄,海马结构的边缘层逐渐变厚;18～22周时,齿状回和海马角折叠进入颞叶,形成C型,海马板层结构变窄.随着孕龄增加,左右两侧HIA线性增大,未发现左右两侧HIA存在性别与半球间差异.结论:7.0T MRI能够清晰显示妊娠中期海马结构的发育变化,并可获得准确的HIA变化数据,这些数据对评价宫内或生后海马结构发育相关疾病有参考意义.

7.0T MRI Study on Development of Fetal Hippocampal Formation in the Second Trimester

Objective：To study the changes of hippocampal formation morphology and its infolding angle during the second trimester and analyze the developmental pattern. Methods：51 fetal specimens （24 males and 27 female） of 14 to 22 weeks gestational age （GA） were selected. All fetuses showed normal central nerve system on sonography examinations. Images were obtained by 7.0T Bruker MRI scanner made in Germany, the morphological changes of the hippocampal formation was analyzed by eFilm software. Hippocampal infolding angle （HIA） was defined as the angle between the line connecting the lateral margin of the cornu ammonis with the medial superior margin of the subiculum and the line passing through the midline structures. The coronal section encompassing the pons was used to perform the measurement of HIA. Results： During 13 -14 weeks GA, there was almost no infolding of hippocampal formation, and the cortex had three layers： periventricular layer, intermediate layer and cortical plate. During 15 -17 weeks GA, dentate gyrus and hippocampal horn started to infold inside the temporal lobe. Hippocampal formation showed typical characteristic of obvious layer structures. Cortex of CA2 and CA3 became narrower while the marginal layer of hippocampal formation became thicker. During 18 -22 weeks GA, dentate gyrus and hippocampal horn had infolded into the temporal lobe and formed a C - type. Layer structures became narrow. Bilateral hippocampal infolding angles increased linearly with GA. No statistically significant difference was noted in gender and hemispheres. Conclusions：7.0T MRI can clearly demonstrate the developmental changes of hippocampal formation, and accurate measurement of the HIA can be obtained with it. The data have reference significance in evaluating the diseases related to the abnormal development of hippocampal formation in vivo or postnatal development.