胎儿大脑皮质层状结构发育的MRI分析

Development of layered structures of fetal cerebral cortex:a MRI study

目的：用3．0T与7．0T胎儿标本MRI分析大脑皮质发育过程中层状结构的变化。方法：46例14~37周胎儿标本，3．0TMRI扫描；并从中选取11例14~27周标本行7．0TMRI扫描，选取不同场强中成像清晰的图像，观察在此阶段内胎脑皮质层状结构的发育变化。结果：在3．0T或7．0T标本MRI上，14～16周时，可观察到4～6层结构；18～23周时，层状结构发育典型，MRI与组织学切片上均显示为7层结构，且此时连续的室周层和外囊纤维可以观察到；24～28周时，层状结构变得不典型；30周后，脑皮质层状结构消失并逐渐成熟。发育中的层状结构在MRI及组织学切片上都以枕叶及海马周围区最明显。3．0TMRTT1加权图像上，不同孕龄皮质下层内正在迁移的丘脑皮质纤维分别显示为其下、中、上部的高信号条带。结论：胎脑皮质层状结构的发育遵循特定时空规律，且应用较高场强的标本MRI冠状位顶枕叶部图像可以最佳的显示其发育变化。

Objective： To analyze the developmental changes of the layered structures of fetal cerebral cortex using 3.0T and 7.0T post-mortem MRI. Methods： Heads of 46 fetal specimens of 14-37 weeks gestational age （GA） were scanned by 3.0T MRI. 11 specimens of 14-27 weeks GA were chosen and scanned by 7.0T MRI. The clearer images were chosen to analyze the developmental changes of the layered structures. Retmlts： On 3.0T or 7.0T post-mortem MRI, 4-6 weeks zones could be recognized at 14~16 weeks GA. During 18-23 weeks GA, the layered structures were typical, 7 zones including periventricular zone and external capsule fibers could be differentiated both on MRI and histological staining slices. During 24-28 weeks GA, layered structures became untypical. After 30 weeks GA, the layered structures disappeared and turned into mature-like tissue gradually. The developing layered structures were the most distinguishable at the parieto-occipital part of the brain and the peripheral region of hippocampus both on MRI and histological staining slices. The migrating thalamocortical afferents appeared as a high signal layer located at the lower, middle, and upper part of the subplate zone respectively on TI images of 3.0T MRI. Conclusions＂ The development of layered structures of fetal cerebral cortex follows a specific spatio-temporal rule, and post-mortem MRI of parieto-occipital part of the brain obtained with higher Tesla is the best to show the developmental changes of layered structures of fetal cerebral cortex.