title: MRI with and without a high-density EEG cap--what makes the difference?
abstract: Besides the benefit of combining electroencephalography (EEG) and magnetic resonance imaging (MRI), much effort has been spent to develop algorithms aimed at successfully cleaning the EEG data from MRI-related gradient and ballistocardiological artifacts. However, there are also studies showing a negative influence of the EEG on MRI data quality. Therefore, in the present study, we focused for the first time on the influence of the EEG on morphometric measurements of T1-weighted MRI data (voxel- and surfaced-based morphometry). Here, we demonstrate a strong influence of the EEG on cortical thickness, surface area, and volume as well as subcortical volumes due to local EEG-related inhomogeneities of the static magnetic (B0) and the gradient field (B1). In a second step, we analyzed the signal-to-noise ratios for both the anatomical and the functional data when recorded simultaneously with EEG and MRI and compared them to the ratios of the MRI data without simultaneous EEG measurements. These analyses revealed consistently lower signal-to-noise ratios for anatomical as well as functional MRI data during simultaneous EEG registration. In contrast, further analyses of T2*-weighted images provided reliable results independent of whether including the individuals' T1-weighted image with or without the EEG cap in the fMRI preprocessing stream. Based on our findings, we strongly recommend against using the structural images obtained during simultaneous EEG-MRI recordings for further anatomical data analysis.
authors.affiliation: Division Neuropsychology, Institute of Psychology, University of Zurich, Zurich, Switzerland. Electronic address: c.klein@psychologie.uzh.ch.
authors.forename: Carina
authors.initials: C
authors.lastname: Klein
authors.affiliation: Division Neuropsychology, Institute of Psychology, University of Zurich, Zurich, Switzerland. Electronic address: j.haenggi@psychologie.uzh.ch.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Hänggi
authors.affiliation: Institute for Biomedical Engineering, University and ETH Zurich, Zurich, Switzerland. Electronic address: luechinger@biomed.ee.ethz.ch.
authors.forename: Roger
authors.initials: R
authors.lastname: Luechinger
authors.affiliation: Division Neuropsychology, Institute of Psychology, University of Zurich, Zurich, Switzerland; International Normal Aging and Plasticity Imaging Center (INAPIC), University of Zurich, Zurich, Switzerland; Center for Integrative Human Physiology (ZIHP), University of Zurich, Zurich, Switzerland; University Research Priority Program (URPP), Dynamic of Healthy Aging, University of Zurich, Zurich, Switzerland; Department of Special Education, King Abdulaziz University, Jeddah, Saudi Arabia. Electronic address: l.jaencke@psychologie.uzh.ch.
authors.forename: Lutz
authors.initials: L
authors.lastname: Jäncke
mesh_terms: D000328:Adult; D016477:Artifacts; D001921:Brain / Q000502:physiology*; D001931:Brain Mapping / Q000295:instrumentation / Q000379:methods; D004569:Electroencephalography / Q000295:instrumentation* / Q000379:methods*; D006801:Humans; D007089:Image Enhancement / Q000295:instrumentation / Q000379:methods; D007090:Image Interpretation, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods*; D008297:Male; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: Chemical shift; Distorted B(0) and B(1) map; Eddy currents; Electroencephalography; Functional and structural magnetic resonance imaging; MRI artifacts; Magnetic susceptibility; SNR; Simultaneous EEG-fMRI