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目的：探讨胎儿颅脑内部主要结构磁共振成像（ＭＲＩ）信号变化的生理意义。方法：采用超导０．３５Ｔ磁共振成像仪，对４２例正常胎儿进行ＭＲＩ成像，观察胎儿颅脑主要结构的信号变化。结果：胎儿的大脑（基底神经核除外）、小脑实质在Ｔ１加权上为略低信号，在质子密度加权上为等信号，在Ｔ２加权上为高信号。脑干、基底神经核在Ｔ１加权上，孕２９周前呈略低信号，孕２９周后呈等信号；在质子密度加权及Ｔ２加权上其信号同大脑、小脑实质信号。脑室信号在ＳＥ序列的所有加权上均呈低信号。结论：在胎儿期，大脑（基底神经核除外）、小脑实质内髓鞘尚未形成，而脑干、基底神经核的髓鞘在孕２９周后形成；胎儿脑脊液的循环速度较成人快，其流速至少４～５ｃｍ／ｓ。
Objective: To investigate the physiological significance of the change of MRI signal in fetal brain. Methods: Forty-two normal fetuses were subjected to MRI imaging with a superconducting 0.35T magnetic resonance imager to observe the signal changes of fetal brain structure. RESULTS: The fetal brain (except basal ganglia), cerebellar parenchyma was a slightly lower signal at T1-weighted, an equal signal at proton density-weighted, and a high signal at T2-weighted. Brainstem and basal ganglia showed slightly lower signal before 29 weeks of gestation on T1-weighted, and equal signals after 29 weeks of gestation. Their signals were similar to those of cerebellum and cerebellum in proton density-weighted and T2-weighted. Ventricular signals showed a low signal on all weights of the SE sequence. CONCLUSION: In the fetal period, the myelin sheath of the cerebellum and basal ganglia is formed after 29 weeks of gestation in the brain (except for the basal nucleus), and the cerebrospinal fluid is circulated faster than adults At least 4 ~ 5cm / s.