1.5T场强下SE、GRE-EPI和弥散加权序列进行脑fMRI的对比研究

A Comparative Study of Brain BOLD fMRI with SE-EPI, GRE-EPI and DWI Sequences at 1.5 Tesla

目的 探讨在 1.5T场强下自旋回波 (SE EPI) ,梯度回波 (GRE EPI)和弥散加权序列检测脑活动的能力。资料与方法 5个右利手健康志愿者 ,在 1.5T场强下通过SE EPI、GRE EPI、弥散加权 (b值 =5 0s/mm2 )序列进行复杂对指运动事件相关性脑功能成像的对比研究 ,采用随机自带的fMRI后处理软件获取功能图像。同时对不同序列所获取的功能信号范围、大小面积和功能信号变化幅度进行t检验。结果 5名志愿者在行复杂对指运动时 ,GRE EPI与SE EPI序列在显示神经元活动的分布范围相似 ,但在显示每个激活区面积 ,GRE EPI显示的明显大于SE EPI(t=- 8.195 ,P <0 .0 1)。GRE EPI和SE EPI序列均显示在刺激与静息间存在明显差异 (tgre=2 .788,Pgre<0 .0 1;tse=- 2 3.2 88,Pse<0 .0 1) ,且两种序列显示的功能信号变化幅度有显著差异 (t=- 9.2 85 ,P <0 .0 1)。而弥散加权序列未能检测出脑功能活动信号。结论 在 1.5T场强下现有的SE或GRE EPI序列均可获取脑功能活动信号 ,GRE EPI序列比SE EPI反映活动神经元敏感性高 。

Objective To evaluate SE-EPI, GRE-EPI and DWI sequences at 1.5 tesla in estimating human brain activities. Materials and Methods Brain BOLD fMRI with SE-EPI, GRE-EPI and DWI (b=50 s/mm 2) sequences at 1.5 tesla was carried out in 5 right-handed healthy volunteers who was performing complex finger-tapping movement during the exam. The functional brain activation was automatically mapped by using the postprocessing software the MR unit carried. The functional signal extent, size and area, as well as the fluctuation range of the signal obtained from different sequences were compared with each other and analyzed by using students' group t test. Results During complex finger-tapping movement, GRE-EPI showed quite the same distribution extent of neuronal activation as SE-EPI did, although the activated area displayed on GRE-EPI was much larger than that displayed on SE-EPI (t=8.195, P<0.01). Significant difference in signal intensity existed between the rest phase and the activation phase on both GRE-EPI (t=2.788, P<0.01) and SE-EPI (t=-23.288, P<0.01). Significant difference in signal fluctuation was also found between SE-EPI and GRE-EPI, with t=-9.285 and P<0.01. DWI could not demonstrate the signal of brain activity. Conclusion At 1.5 tesla, event-related brain activation signal can be documented by both SE-EPI and GRE-EPI BOLD fMRI. GRE-EPI is more sensitive than SE-EPI in detecting neuronal activation as GRE-EPI can get the signal from the large draining vein.