颈部脊髓静息态血氧水平依赖对比功能性磁共振成像信号的频域分析

Frequency domain analysis of MR signals detected in human cervical spinal cord with blood oxygen level dependent functional magnetic resonance imaging

首先对2例健康受试者进行组块设计的运动任务颈段脊髓血氧水平依赖对比功能性磁共振成像成像,采用SPM5软件包分析,观察运动任务引发的血氧水平依赖信号强度。之后对10例受试者进行静息状态下颈段脊髓血氧水平依赖对比功能性磁共振成像,采用GIFT软件进行独立成分分析,观察不同强度信号(±4%范围之内和±20%范围之外)的频域分布特征。信号变化强度在±4%范围之内的独立成分,频域分布主要集中在约0.1Hz带宽,在约0.8Hz带宽也较为集中;信号变化强度超过±20%范围的独立成分,频域分布主要集中在约1.0Hz带宽,在约0.3Hz带宽也较为集中。结果提示,静息态脊髓血氧水平依赖成像的高波幅变化信号主要来源于心跳和呼吸造成的运动伪迹;典型血氧水平依赖信号变化波幅范围内的独立成分,部分来源于心跳和呼吸运动交互作用产生的运动伪迹,其他成分的来源需要进一步研究。

Two male healthy subjects received functional magnetic resonance imaging （fMRI） examination in a 1.5 T GE MR scanner with block-designed method. Blood oxygen level dependent （BOLD） weighted functional images from C5 to T1 vertebral levels were acquired in the axial plane. Two different motor tasks were employed. Data were analyzed with SPM5 software package to acquire magnitudes of BOLD signal changes. Then 10 male healthy subjects in resting state received fMRI examination. Functional MRI data were analyzed with SPM5 and GIFT. Features in frequency domain of MR signals with different magnitudes （within ＋4% or beyond the range of ＋20%） were studied. MR signal changes within ＋4% magnitudes were found to occur mainly in the frequency bandwidth 0.1 Hz and 0.8 Hz. MR signal changes beyond the range of ＋20% were found to occur mainly in the frequency bandwidth 1.0 Hz and 0.3 Hz. The result demonstrated that MR signal changes with high magnitudes detected in human cervical spinal cord in resting state stemmed mainly from cardiac and respiratory motion. MR signal changes within bandwidth in accordance with that of interaction of cardiac and respiratory processes were observed from signals with typical range of BOLD signal fluctuations, origins of other detected MR signal changes needed to be investigated in further studies.