20周胎儿标本脑组织MRI显示与三维可视化分析

目的：探讨20周胎儿脑标本MRI显示的发育情况及其三维可视化分析。方法：对8例20周胎儿脑标本行3.0TMR扫描，其中2例加行7.0TMR扫描。选取不同场强、方位的MR图像，分析其发育中的脑结构在MRI上的显示状况。选取1例冠状位7.0TMR图像，应用Amira4.1软件进行分割并三维重建。结果：3.OT与7.0TMRI显示，20周胎儿大部分脑沟雏形已经形成，表现为皮质表面的浅或宽凹陷；皮质层状结构发育典型，呈现为信号不同的堆积条带，以顶枕叶及海马区最为典型；基底核团可以分辨，其间界线与内外囊清晰。7.0TMRI显示脑干与小脑已具备典型成人外观，并可见其内部结构；在其三维重建图像上，可观察到皮质表面幼稚脑沟的深度、长度及所处位置，端脑、脑干与小脑外形及其位置关系都可以得到较好显示。结论：20周时，胎脑已完成初始阶段的发育，并具备成熟脑结构外观，这些结构在3.0T与7.0TMRI上，尤其是7.0TMRI上均得以清晰显示。三维可视化有助于对幼稚脑结构的宏观认识。

MRI and Three-dimensional Visualization Analysis of Fetal Brain at 20-week Gestational Age

Objective： To explore the developmental condition of fetal brain at 20-weeks gestational age （GA） by magnetic resonance imaging （MRI） and three-dimensional visualization. Methods： Eight fetal brains at 20-weeks GA were scanned by 3.0T MR, among which two specimens were scanned by 7.0T MR. The developmental condition of brain tissue was analyzed by selecting various strength and orientation of MRI images. The coronal 7.0T MRI of one specimen was selected for three-dimensional reconstruction by using Amira 4.1 software. Results ：3.0T and 7.0T MRI showed that most cortical sulci had been present but were immature, characterized as shallow or broad fossas on cerebral surface. The lamellar structures of cerebral cortex developing typically, displayed accumulated straps with different signals, the most typical was seen in parieto-occipital lobes and hippocampal regions. The basal nucleus was distinguishable and had a clear boundary with internal and external capsule. The 7.0T MRI showed that the brain stem and cerebellum had a typical appearance of adult, the internal structures could be seen. The three-dimensional reconstructed images displayed the depth, length and position of the immature cortical sulci on the surface of cerebral cortex. Meanwhile, the shapes and locations of telencephalon, brain stem and cerebellum were exhibited clearly. Conclnsions：The ini- tial developmental stages of fetal brain have been completed, and with a mature appearance of brain structure at 20 - week GA. These structures in 3. OT and 7. OT MRI, especially in 7.0T MR! can be clearly shown. In ad- dition, the three - dimensional visualization contributes to macroscopic understanding of immature brain struc-ture.