正常胎儿脑形态和髓鞘形成的MRI以及弛豫时间测量

MR Imaging of Brain Morphology and Myelination and Relaxation Time Measurement in Normal Fetuses

目的 :评价胎脑形态学和髓鞘形成过程的MR成像 ,对胎脑弛豫时间进行测量。材料和方法 :正常胎脑标本 3 2例 ,胎龄 16～ 3 9周。对胎脑形态以及 8个解剖区的信号强度进行了评价 ;对脑灰、白质的T1和T2弛豫时间进行了测量并对数据进行统计学分析。结果 :MR成像能很好地显示某些脑裂、脑沟及脑回按时间依次出现的过程 ;髓鞘形成过程发生较早 ,呈现为向头端有序的变化方式 ;胎儿脑白质的T1和T2弛豫时间明显长于灰质的T1和T2弛豫时间。结论 :MR成像可用于评价胎脑形态及髓鞘形成 ;胎脑含水量持续高于成人脑含水量 ,水在胎脑灰、白质中的分布与成人不同。

Purpose: To evaluate the fetal brain morphology and myelination process, and to measure the fetal brain relaxation times by using magnetic resonance (MR) imaging of the fetal brain. Materials and Methods: Thirty two normal fetal specimens, 16～39 week's gestational age, were studied by MR imaging. The fetal brain morphology and the signals in 8 anatomic areas were evaluated. T1 and T2 relaxation times of gray and white matter were measured and the data were statistically analyzed. Results: Various fissures, sulci and gyri of the fetal brain appeared sequentially according to the chronological stages and were demonstrated very well on MR imaging. Myelination process occurred early in the fetal stage and proceeded cephalad in an orderly fashion. The T1 and T2 relaxation times of the white matter were statistically longer than that of the gray matter throughout the developing period. Conclusion: The fetal brain morphology and myelination can be clearly demonstrated and evaluated by MR imaging. The water content of the fetal brain is persistently higher than that of the adult brain, and the water distribution in the fetal gray and white matter is different from the situation in normal adults.