EPI序列的TE参数对功能磁共振成像激活信号的影响

Effects of echo time on BOLD signal using single shot gradient echo planer scan sequence

目的 :探讨使用单次激励平面回波成像 (EPI)序列行功能磁共振成像 (fMRI)时 ,回波时间 (TE)对脑区激活信号的影响。方法 :正常被试者 7例 ,年龄 2 1.5～ 3 8.0岁 ,均为右利手。采用事件相关 (ER)设计方法 ,任务为右侧手指弹钢琴样序列运动。使用不同的TE时间进行EPI序列扫描 ,用SPM99软件包对扫描数据进行t检验以获取执行任务与静息状态对比的脑功能图像。比较TE 45ms、TE 5 5ms、TE 60ms时脑内运动区的血氧水平依赖对比的fMRI信号变化。结果 :3组不同TE情况下 ,以TE 45ms所获取的激活信号最强 ,最符合公认的激活部位。TE 5 5ms及 60ms所获得的激活信号均较弱。结论 :随TE不同 ,梯度EPI序列获取的fMRI激活信号大小及强度亦有改变 ,以TE为 45ms时得到的激活信号强度、范围及部位最佳。

Objective:To assess the effect of echo time (TE) on blood oxygenation level dependent contrast (BOLD) signal using single shot gradient echo planner scan sequence in functional MR.Methods:Event related (ER) designed BOLD functional MRI scans covering the main motor areas were performed on 7 volunteers aged 21.5～38.0 years old.Executing right fingers flip by cues like playing the piano served as stimuli for all subjects.fMRI scans were performed stochastically using 3 different TE 45ms,55ms and 60ms,respectively.The other scan parameters were unchanged.The fMRI data were analyzed by using SPM99 (Statistical Parametric Mapping) software with statistic test to generate the activation map. Results: fMRI scan with TE 45ms induced the most sufficient activation map in motor area,compared to those with TE of 55ms and 60ms.Conclusion:The size,location,and intensities of BOLD signals varied in gradient EPI sequences with different echo time.45ms was the most appropriate echo time for obtaining sufficient BLOD signal.