Simultaneous EEG-fMRI: Evaluating the Effect of the EEG Cap-Cabling Configuration on the Gradient Artifact
Simultaneous EEG-fMRI: Evaluating the Effect of the EEG Cap-Cabling Configuration on the Gradient Artifact
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DOI：
10.3389/fnins.2019.00690
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发表时间：
2019-07-10
影响因子：
4.3
通讯作者：
Bowtell, Richard
中科院分区：
文献类型：
--
作者：
Chowdhury, Muhammad E. H.;Khandakar, Amith;Bowtell, Richard
在同步EEG-fMRI实验中记录的脑电图（EEG）数据被大梯度伪影（GA）污染。GA的振幅取决于EEG导联形成的线圈面积以及磁场梯度的切换速率，这对于MR成像至关重要。平均伪影减法（AAS）是GA校正最常用的方法，它依赖于EEG放大器具有足够大的动态范围来表征伪影电压。低通滤波（250 Hz截止）通常用于衰减GA的高频电压波动，但即使采取这种预防措施，也可能发生通道饱和，特别是在采集高空间分辨率MRI数据期间。以前的工作表明，带状电缆，用于连接EEG帽和放大器，使一个显着的贡献，遗传算法，因为电缆的几何形状产生大的有效线环面积。然而，通过适当地将带状电缆的电线连接到EEG帽，应该可以通过产生帽和电缆贡献的部分抵消来最小化GA的总体范围和均方根（RMS）幅度。在这里，通过修改EEG帽与1 m带状电缆的连接，我们能够将用于高分辨率冠状回波平面成像（EPI）采集的GA的范围减小约1.6倍，并将用于标准轴向EPI采集的GA的范围减小约1.15倍。这些变化可能会被转化为所需的动态范围的减少，在EEG带宽的增加或在不饱和的情况下可实现的图像分辨率的增加，所有这些都可以在EEG-fMRI研究中被有益地利用。重新布线还可以防止系统在使用标准记录带宽发生小的受试者移动时饱和。
Electroencephalography (EEG) data recorded during simultaneous EEG-fMRI experiments are contaminated by large gradient artifacts (GA). The amplitude of the GA depends on the area of the wire loops formed by the EEG leads, as well as on the rate of switching of the magnetic field gradients, which are essential for MR imaging. Average artifact subtraction (AAS), the most commonly used method for GA correction, relies on the EEG amplifier having a large enough dynamic range to characterize the artifact voltages. Low-pass filtering (250 Hz cut-off) is generally used to attenuate the high-frequency voltage fluctuations of the GA, but even with this precaution channel saturation can occur, particularly during acquisition of high spatial resolution MRI data. Previous work has shown that the ribbon cable, used to connect the EEG cap and amplifier, makes a significant contribution to the GA, since the cable geometry produces large effective wire-loop areas. However, by appropriately connecting the wires of the ribbon cable to the EEG cap it should be possible to minimize the overall range and root mean square (RMS) amplitude of the GA by producing partial cancelation of the cap and cable contributions. Here by modifying the connections of the EEG cap to a 1 m ribbon cable we were able to reduce the range of the GA for a high-resolution coronal echo planar Imaging (EPI) acquisition by a factor of similar to 1.6 and by a factor of similar to 1.15 for a standard axial EPI acquisition. These changes could potentially be translated into a reduction in the required dynamic range, an increase in the EEG bandwidth or an increase in the achievable image resolution without saturation, all of which could be beneficially exploited in EEG-fMRI studies. The re-wiring could also prevent the system from saturating when small subject movements occur using the standard recording bandwidth.