Vincent Justin L, Larson-Prior Linda J, Zempel John M, Snyder Abraham Z
Department of Radiology, Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, MO 63110, USA.
Clin Neurophysiol. 2007 May;118(5):981-98. doi: 10.1016/j.clinph.2006.12.017. Epub 2007 Mar 26.
Simultaneous acquisition of electroencephalogram (EEG) and functional magnetic resonance imaging (fMRI) enables studies of brain activity at both high temporal and high spatial resolution. However, EEG acquired in a magnetic field is contaminated by ballistocardiogram (BKG) artifact. The most commonly used method of BKG artifact reduction, averaged artifact subtraction (AAS), was not designed to account for overlapping BKG waveforms generated by adjacent beats. We describe a new method based on a moving general linear model (mGLM) that accounts for overlapping BKG waveforms.
Simultaneous EEG-fMRI at 3 Tesla was performed in nine normal human subjects (8-11 runs/subject, 5.52 min/run). Gradient switching artifact was effectively reduced using commercially supplied procedures. Cardiac beats were detected using a novel correlation detector algorithm applied to the EKG trace. BKG artifact was reduced using both mGLM and AAS.
mGLM recovered BKG waveforms outlasting the median inter-beat interval. mGLM more effectively than AAS removed variance in the EEG attributable to BKG artifact.
mGLM offers advantages over AAS especially in the presence of variable heart rate.
The BKG artifact reduction procedure described herein improves the technique of simultaneous EEG-fMRI. Potential applications include basic investigations of the relationship between scalp potentials and functional imaging signals as well as clinical localization of epileptic foci.
同步采集脑电图（EEG）和功能磁共振成像（fMRI）能够在高时间分辨率和高空间分辨率下研究大脑活动。然而，在磁场中采集的脑电图会受到心冲击图（BKG）伪迹的干扰。最常用的减少BKG伪迹的方法，即平均伪迹减法（AAS），并未设计用于处理相邻心跳产生的重叠BKG波形。我们描述了一种基于移动通用线性模型（mGLM）的新方法，该方法可处理重叠的BKG波形。
对9名正常人类受试者进行了3特斯拉的同步EEG-fMRI检查（每位受试者8 - 11次扫描，每次扫描5.52分钟）。使用商业提供的程序有效减少了梯度切换伪迹。使用一种应用于心电图轨迹的新型相关检测算法检测心跳。使用mGLM和AAS减少BKG伪迹。
mGLM恢复了持续时间超过心跳间隔中位数的BKG波形。mGLM比AAS更有效地去除了脑电图中由BKG伪迹引起的方差。
mGLM相对于AAS具有优势，特别是在心率可变的情况下。
本文所述的减少BKG伪迹的程序改进了同步EEG-fMRI技术。潜在应用包括头皮电位与功能成像信号之间关系的基础研究以及癫痫病灶的临床定位。
