1.5T磁共振仪评估新生儿和婴儿的正常脑髓鞘

Evaluation of Normal Maturation of the Neonatal and Infant Brain with 1.5T MRI

目的 应用高场MR仪研究正常小儿不同月龄段的脑髓鞘与对应MRI信号特征。材料与方法 72例正常小儿在 1.5TMR仪行头部扫描。采用自旋回波 (SE)和快速自旋回波 (TSE)序列 ,获取T1和T2 加权像。结果 (1)髓鞘形成中的MRI信号变化 :相对于灰质信号 ,未成熟的髓鞘呈短T1和长T2 ,在T1WI上呈高信号与灰质易区别 ;在T2 WI上与灰质信号相近 ,成熟的髓鞘呈短T1和短T2 ,在T2 WI上呈低信号 ,与灰质易区别。(2 )髓鞘形成至成熟时间 :小脑上下脚、桥脑背侧、丘脑腹外侧核和内囊后肢后部出生时已成熟 ,小脑自出生～ 5个月 ,小脑中脚 2～ 4个月 ,内囊前肢 3～ 7个月 ,胼胝体后部、膝部分别是 3～ 5个月、4～ 7个月 ,半卵圆中心 2～ 7个月 ,枕顶叶白质 3～ 9个月 ,额颞叶白质 4～ 12个月。结论 不同月龄段不同解剖部位正常脑髓鞘化具有各自MRI信号特征 ,有利于评判是否脑发育正常和患脑白质病 ,T1WI评估未成熟髓鞘较好 ,T2 WI确定髓鞘是否成熟较好。

Objective To study MRI features of normal brain myelinization in neonates and infants at their various stages of development. Materials and Methods MR scanning of the brain using SE and TSE sequences with a 1.5T unit was performed in 72 normal cases (aged 0～2 years) without significant neurological symptoms. Myelinization on both T 1WI and T 2WI at various stages of development was observed.Results (1) Compared with gray-matter signal intensity, immature myelin carried short T 1 and long T 2 relaxation time, while matured myelin carried short T 1 and short T 2 relaxation time. (2) Myelinization process was observed in seventeen areas in the brain. The myelinic matured age of the different parts of the brain was different. The cerebellar white matter was matured right at birth. The cerebellum became matured at the age of 5 months, while the middle cerebellar peduncle at 2～4 months, the anterior limb of internal capsule at 3～7 months, the splenium and genu of corpus callosum at 3～5 and 4～7 months respectively, the centrum semiovale at 2～7 months, the white matter of parietal-occipital area at 3～9 months, and the white matter of the frontal-temporal area at 4～12 months.Conclusion Characteristic MR signal intensity is helpful to differentiate normal from abnormal brain maturation. T 1WI is more useful in detecting immature myelin while T 2WI is more helpful in judging the maturation of the myelin.