7.0T磁共振BOLD技术评估大鼠脊髓损伤功能继发性改变的研究

摘要

Objective:To explore the imaging trends of secondary brain function changes in resting state and task state after spinal cord injury (SCI) in rats using the blood oxygenation level dependent functional magnetic resonance imaging (BOLD-fMRI).Methods:Complete spinal cord transected injury model was established in 12 SD rats,and categorized as Stage A,B and C according to the stimulation time after modeling.Stage A,as a control,performed after 5 minutes of modeling,the electrodes were inserted into the muscle at 2 mm on the right side of the spinal cord.Stage B,after 30 minutes of modeling,the electrodes were inserted into the lower section of the spinal cord at about 2 mm.Stage C,after 24 hours of modeling,the electrodes were inserted into the lower section of the spinal cord at about 2 mm.The resting and task state 7.0T fMRI was performed for all stages of the rats,and the electrical stimulation (0.5 A,1 Hz) in task state lasted about 320 seconds.SPM8 and DPARSF software were used to analyze the task state and resting state fMRI data.Results:There were significant differences in the resting state and task state brain activity for the three stages.The resting brain activity areas of rats were mainly located in the prefrontal lobe,anterior cingulate gyrus and hippocampus.The number of active voxels in stage B increased by 10％ compared with that in stage A,and the fractional amplitude of low-frequency fluctuations(fALFF)increased by 21％;the number of active voxels in stage C decreased by 4.4％ compared with that in stage A,fALFF decreased by 6％.The brain activation areas of the task states in the three periods included the precentral gyrus,the postcentral gyrus,and the striatum.The number of active voxels in stage B decreased by 64％ compared with that in stage A,and the mean value of t value decreased by 49％.The number of active voxels in stage C increased by 61％ compared with that in stage A,and the mean value of t value decreased by 9％.Conclusion:BOLD-fMRI can dynamically,quantitatively and noninvasively evaluate the secondary changes of brain function activity in resting and task state after SCI in rats in vivo.After SCI,there is a stress effect in the static brain function,which disappears after 24 hours.After SCI,the activation of the brain function in the task state is from low level to high level.%目的:基于血氧水平依赖功能磁共振(Blood oxygenation level dependent functional magnetic resonance imaging,BOLD-fMRI)方法探讨大鼠脊髓损伤后(Spinal cord injury,SCI)静息态及任务态的脑功能活动继发性改变的影像学趋势.方法:12只SD大鼠每只按造模后刺激时间顺序分为A、B、C三个时期.A期作为对照,造模后5 min电极插入脊髓右侧肌肉2 mm处;B期为造模30 min后电极插入脊髓横断面下段约2 mm处;C期为造模24 h后电极插入脊髓横断面下段约2 mm处.各期大鼠行静态和任务态7.0T磁共振fMRI成像,其中任务态电刺激(0.5 A,1 Hz)持续320 s.采用SPM8及DPARSF软件分析任务态及静息态fMRI数据.结果:A、B、C三种时期的大鼠静息态和任务态的脑活动水平存在明显差异.大鼠静息态脑活动区主要分布在前额叶中部、前后扣带回和海马.其中,B期较A期活动体素数量上升10％,低频振幅比率分数(fALFF)上升21％;C期较A期活动体素数量下降4.4％,fALFF下降6％.三个时期大鼠任务态的脑激活区主要包括中央前回、中央后回、纹状体.其中,B期较A期激活体素数量下降64％,t值平均值下降49％;C期较A期激活体素数量上升61％,t值平均值下降9％.结论:应用BOLD-fMRI方法可活体动态、定量、无创评估大鼠SCI后静息态及任务态的脑功能活动继发性改变,SCI后静息态脑功能活动存在一个应激效应,而这种应激效应在24 h后消失,SCI后任务态脑功能激活存在由低到高的过程.