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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,3.0T MRI扫描;并从中选取11例14~27周标本行7.0T MRI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。3.0T MRI T1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 changes of lamellar structure during the development of cerebral cortex with 3.0T and 7.0T fetuses. Methods: Forty-six fetuses from 14 to 37 weeks were scanned with 3.0T MRI. Seventeen fourteen to twenty-seven week-old fetuses were scanned by 7.0T MRI. The images of clear field in different field intensity were selected to observe the changes of fetal brain cortex Structural changes. Results: On the 3.0T or 7.0T MRI specimens, 4 ~ 6 layers were observed at 14 ~ 16 weeks. At 18 ~ 23 weeks, the lamellar structure was typical. The MRI and histological sections showed 7 layers Structure, and at this time the continuous ventricular and outer capsule fibers can be observed; 24 to 28 weeks, the layered structure becomes atypical; 30 weeks later, the cortical layer structure disappears and gradually mature. Layered structures in development in the MRI and histological sections of the occipital lobe and hippocampus around the most obvious area. On the 3.0T MRI T1-weighted images, the migrating thalamic cortical fibers in different gestational age subcortical layers showed high signal bands at the lower, middle and upper, respectively. CONCLUSION: The development of fetal cerebral cortical laminar structure follows a specific temporal and spatial pattern. The higher occipital lobe images of coronal and superior occipital lobes can best show the developmental changes.