Simultaneous EEG-fMRI at ultra-high field: Artifact prevention and safety assessment
Simultaneous EEG-fMRI at ultra-high field: Artifact prevention and safety assessment
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DOI：
10.1016/j.neuroimage.2014.10.055
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发表时间：
2015-01-15
期刊：
影响因子：
5.7
通讯作者：
Gruetter, Rolf
中科院分区：
文献类型：
--
作者：
Jorge, Joao;Grouiller, Frederic;Gruetter, Rolf
同时记录头皮脑电(EEG)和功能磁共振成像(FMRI)可以为人类大脑功能的动态提供独特的见解，而超高场fMRI提供的更高的功能灵敏度为这种多模式方法的未来开辟了令人兴奋的前景。然而，同时记录容易受到各种伪影的影响，其中许多伪影随磁场强度而变化，并且在3T以上的记录中会严重影响EEG和fMRI数据质量。本研究的目的是在7T的人类中实现和表征同时EEG-fMRI的优化设置。在模体模型中评估了用于帽和放大器之间信号传输的EEG电缆长度和几何形状的影响，并特别关注来自MR扫描仪冷头的噪声贡献。电缆缩短(从线帽到放大器最小为12厘米)和捆绑有效地降低了环境噪声，平均功率降低了84%，通道间功率变化性降低了91%。通过在体模模型上对射频功率分布和温度测量的数值模拟，基于现有的有限的超高场文献，对受试者的安全性进行了评估和确认。通过对一名志愿者的B-0和B-1(+)场映射来表征由于EEG系统引起的MRI数据退化效应，显示了重要的但不是禁止的B1干扰效应。在优化的设置下，5名健康志愿者同时进行了EEG-fMRI采集，他们接受了两种视觉范式：睁眼/闭眼任务和使用反转棋盘刺激的视觉诱发电位(VEP)范式。脑电数据分别显示清晰的枕叶阿尔法调制和平均VEP，并伴随着大胆的信号变化。在单一试验水平上，可以相对可信地在所有试验中观察到阿尔法功率变化；VEP检测更为有限，尽管在每个受试者的50%以上的试验中可以检测到统计上显著的反应。总体而言，我们得出的结论是，建议的设置非常适合在7 T。(C)2014 Elsevier Inc.保留所有权利。
The simultaneous recording of scalp electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) can provide unique insights into the dynamics of human brain function, and the increased functional sensitivity offered by ultra-high field fMRI opens exciting perspectives for the future of this multimodal approach. However, simultaneous recordings are susceptible to various types of artifacts, many of which scale with magnetic field strength and can seriously compromise both EEG and fMRI data quality in recordings above 3 T. The aim of the present study was to implement and characterize an optimized setup for simultaneous EEG-fMRI in humans at 7 T. The effects of EEG cable length and geometry for signal transmission between the cap and amplifiers were assessed in a phantom model, with specific attention to noise contributions from the MR scanner coldheads. Cable shortening (down to 12 cm from cap to amplifiers) and bundling effectively reduced environment noise by up to 84% in average power and 91% in inter-channel power variability. Subject safety was assessed and confirmed via numerical simulations of RF power distribution and temperature measurements on a phantom model, building on the limited existing literature at ultra-high field. MRI data degradation effects due to the EEG system were characterized via B-0 and B-1(+) field mapping on a human volunteer, demonstrating important, although not prohibitive, B1 disruption effects. With the optimized setup, simultaneous EEG-fMRI acquisitions were performed on 5 healthy volunteers undergoing two visual paradigms: an eyes-open/eyes-closed task, and a visual evoked potential (VEP) paradigm using reversing-checkerboard stimulation. EEG data exhibited clear occipital alpha modulation and average VEPs, respectively, with concomitant BOLD signal changes. On a single-trial level, alpha power variations could be observed with relative confidence on all trials; VEP detection was more limited, although statistically significant responses could be detected in more than 50% of trials for every subject. Overall, we conclude that the proposed setup is well suited for simultaneous EEG-fMRI at 7 T. (C) 2014 Elsevier Inc. All rights reserved.