MRI-compatible EEG Research Articles

Practicality and cost-effectiveness of using MRI compatible EEG system in the critical care setting

BackgroundContinuous video-EEG (cvEEG) monitoring is a vastly utilized tool for monitoring critically ill patients in the intensive care unit. Our study investigates the clinical utility and cost-effectiveness of using MRI Compatible EEG electrode system for patients being monitored in the intensive care unit. MethodsThis retrospective study included 14 critically ill patients who underwent cvEEG between March 2019 to March 2020. They were classified into 2 subgroups: Group 1- ‘MRI-compatible EEG’ (mean age: 56.00 ± 19.99 years; M:F = 2:5; N = 7), Group 2 – ‘Conventional EEG’ (mean age: 49.14 ± 24.76 years; M:F = 4:3; N = 7). The EEG monitoring times as well as cost-effectiveness of cvEEG between the groups were compared using Mann-Whitney Test (p ≤ 0.05). We also compared the MRI quality between the groups using Chi-squared test (p ≤ 0.05). ResultsThe EEG non-monitored time in Group 2 (7.62 ± 6.45 h) was significantly higher than Group 1 (2.71 ± 2.34 h)] (p = 0.025). The average daily cost for cvEEG in Group 1 ($2098.53 ± 493.58) and Group 2 ($2230.58 ± 142.73) was comparable (p = 0.896). The quality of MRI scans between Group 1 (6/7) and 2 (6/7) were also comparable (p = 1.000). ConclusionsThe monitoring time lost in patients with MRI Compatible EEG electrodes was significantly lower than the patients with Conventional EEG electrodes. The daily cost of monitoring and the quality of MRI scans were comparable between the 2 groups. We conclude that the use of MRI Compatible EEG electrodes is a practical and cost-effective method to improve the quality of monitoring in critically ill patients.

Abnormal Brain Network Topology During Non-rapid Eye Movement Sleep and Its Correlation With Cognitive Behavioral Abnormalities in Narcolepsy Type 1.

Objective: Simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) were applied to investigate the abnormalities in the topological characteristics of functional brain networks during non-rapid eye movement(NREM)sleep. And we investigated its relationship with cognitive abnormalities in patients with narcolepsy type 1 (NT1) disorder in the current study.Methods: The Beijing version of the Montreal Cognitive Assessment (MoCA-BJ) and EEG-fMRI were applied in 25 patients with NT1 and 25 age-matched healthy controls. All subjects participated in a nocturnal video polysomnography(PSG)study, and total sleep time (TST), percentage of TST (%TST) for each sleep stage and arousal index were calculated. The Epworth Sleepiness Score (ESS) was used to measure the degree of daytime sleepiness. The EEG-fMRI study was performed simultaneously using a 3T MRI system and a 32-channel MRI-compatible EEG system during sleep. Visual scoring of EEG data was used for sleep staging. Cognitive function was assessed for all subjects using the MoCA-BJ. The fMRI data were applied to establish a whole-brain functional connectivity network for all subjects, and the topological characteristics of the whole-brain functional network were analyzed using a graph-theoretic approach. The topological parameters were compared between groups. Lastly, the correlation between topological parameters and the assessment scale using Montreal Cognition was analyzed.Results: The MoCA-BJ scores were lower in patients with NT1 than in normal controls. Whole-brain global efficiency during stage N2 sleep in patients with NT1 displayed significantly lower small-world properties than in normal controls. Whole-brain functional network global efficiency in patients with NT1 was significantly correlated with MoCA-BJ scores.Conclusion: The global efficiency of the functional brain network during stage N2 sleep in patients with NT1 and the correspondingly reduced small-world attributes were associated with cognitive impairment.

Adapted cabling of an EEG cap improves simultaneous measurement of EEG and fMRI at 7T

BackgroundThe combination of EEG and ultra-high-field (7 T and above) fMRI holds the promise to relate electrophysiology and hemodynamics with greater signal to noise level and at higher spatial resolutions than conventional field strengths. Technical and safety restrictions have so far resulted in compromises in terms of MRI coil selection, resulting in reduced, signal quality, spatial coverage and resolution in EEG-fMRI studies at 7 T. New methodWe adapted a 64-channel MRI-compatible EEG cap so that it could be used with a closed 32-channel MRI head coil thus avoiding several of these compromises. We compare functional and anatomical as well as the EEG quality recorded with this adapted setup with those recorded with a setup that uses an open-ended 8-channel head-coil. ResultsOur set-up with the adapted EEG cap inside the closed 32 channel coil resulted in the recording of good quality EEG and (f)MRI data. Both functional and anatomical MRI images show no major effects of the adapted EEG cap on MR signal quality. We demonstrate the ability to compute ERPs and changes in alpha and gamma oscillations from the recorded EEG data. Comparison with existing methodsCompared to MRI recordings with an 8-channel open-ended head-coil, the loss in signal quality of the MRI images related to the adapted EEG cap is considerably reduced. ConclusionsThe adaptation of the EEG cap permits the simultaneous recording of good quality whole brain (f)MRI data using a 32 channel receiver coil, while maintaining the quality of the EEG data.

Abnormal Thalamic Functional Connectivity During Light Non–Rapid Eye Movement Sleep in Children With Primary Nocturnal Enuresis

To investigate abnormalities of thalamocortical and intrathalamic functional connectivity (FC) in children with primary nocturnal enuresis (PNE) during light non-rapid eye movement (NREM) sleep using a simultaneous electroencephalography (EEG)-functional magnetic resonance imaging (fMRI) method. Polysomnographic and EEG-fMRI data were obtained during sleep from 61 children with PNE (age 10.2 ± 1.7 years, 59% boys) and 61 age-matched controls (age 10.1 ± 1.4 years, 54% boys). All subjects first participated in one overnight video-polysomnographic study. Total sleep time, percentage of total sleep time in each sleep stage, arousal index, and awakening index were calculated. Simultaneous EEG-fMRI studies were then performed using a 3T MRI system with a 32-channel MRI-compatible EEG system. Visual scoring of EEG data permitted sleep staging. Thalamocortical and intrathalamic FCs in the waking state and at different stages of light sleep were calculated and compared. Children with PNE had a higher percentage of total sleep time in light sleep and a higher arousal index compared with controls. Abnormal thalamocortical FCs were detected in the lateral prefrontal cortex, medial prefrontal cortex, and inferior parietal lobule during light NREM sleep. Abnormal intrathalamic FCs were also detected during light NREM sleep among the motor, occipital, prefrontal, and temporal subdivisions of the thalamus. Abnormal prefrontal and parietal thalamocortical FCs, accompanied by abnormal intrathalamic FCs among the motor, occipital, prefrontal, and temporal subdivision of thalamus during light NREM sleep, may be related to abnormal sleep and enuresis in children with PNE.

Effects of A 60 Hz Magnetic Field of Up to 50 milliTesla on Human Tremor and EEG: A Pilot Study.

Humans are surrounded by sources of daily exposure to power-frequency (60 Hz in North America) magnetic fields (MFs). Such time-varying MFs induce electric fields and currents in living structures which possibly lead to biological effects. The present pilot study examined possible extremely low frequency (ELF) MF effects on human neuromotor control in general, and physiological postural tremor and electroencephalography (EEG) in particular. Since the EEG cortical mu-rhythm (8–12 Hz) from the primary motor cortex and physiological tremor are related, it was hypothesized that a 60 Hz MF exposure focused on this cortical region could acutely modulate human physiological tremor. Ten healthy volunteers (age: 23.8 ± 4 SD) were fitted with a MRI-compatible EEG cap while exposed to 11 MF conditions (60 Hz, 0 to 50 mTrms, 5 mTrms increments). Simultaneously, physiological tremor (recorded from the contralateral index finger) and EEG (from associated motor and somatosensory brain regions) were measured. Results showed no significant main effect of MF exposure conditions on any of the analyzed physiological tremor characteristics. In terms of EEG, no significant effects of the MF were observed for C1, C3, C5 and CP1 electrodes. However, a significant main effect was found for CP3 and CP5 electrodes, both suggesting a decreased mu-rhythm spectral power with increasing MF flux density. This is however not confirmed by Bonferroni corrected pairwise comparisons. Considering both EEG and tremor findings, no effect of the MF exposure on human motor control was observed. However, MF exposure had a subtle effect on the mu-rhythm amplitude in the brain region involved in tactile perception. Current findings are to be considered with caution due to the small size of this pilot work, but they provide preliminary insights to international agencies establishing guidelines regarding electromagnetic field exposure with new experimental data acquired in humans exposed to high mT-range MFs.

Simultaneous EEG-fMRI for working memory of the human brain.

Memory plays an important role in human life. Memory can be divided into two categories, i.e., long term memory and short term memory (STM). STM or working memory (WM) stores information for a short span of time and it is used for information manipulations and fast response activities. WM is generally involved in the higher cognitive functions of the brain. Different studies have been carried out by researchers to understand the WM process. Most of these studies were based on neuroimaging modalities like fMRI, EEG, MEG etc., which use standalone processes. Each neuroimaging modality has some pros and cons. For example, EEG gives high temporal resolution but poor spatial resolution. On the other hand, the fMRI results have a high spatial resolution but poor temporal resolution. For a more in depth understanding and insight of what is happening inside the human brain during the WM process or during cognitive tasks, high spatial as well as high temporal resolution is desirable. Over the past decade, researchers have been working to combine different modalities to achieve a high spatial and temporal resolution at the same time. Developments of MRI compatible EEG equipment in recent times have enabled researchers to combine EEG-fMRI successfully. The research publications in simultaneous EEG-fMRI have been increasing tremendously. This review is focused on the WM research involving simultaneous EEG-fMRI data acquisition and analysis. We have covered the simultaneous EEG-fMRI application in WM and data processing. Also, it adds to potential fusion methods which can be used for simultaneous EEG-fMRI for WM and cognitive tasks.

P184: Activity and functional connectivity of the premotor-parietal network modulate intrinsic power changes of mu rhythms: an EEG-fMRI study

P185 – Figure 1. A. Brain regions more activated when using tools compared to neutral objects (bars) in fMRI study with healthy controls. B. Statistical map of the voxels associated with tool use scoring in LBD patients in lesion analyse study using VLSM. acquired brain activity from fifteen healthy participants (age range 21-35), by combining 32-channel MRI-compatible EEG and Siemens 3T-MRI systems. During data acquisition, the participants were awake and not engaged in any tasks with their eyes closed. BOLD-based fMRI signals and surface EEG data were recorded simultaneously for 20 min. Power of mu rhythms was calculated from EEG data at C3 and C4 electrodes within a 3-second time bin, corresponding to a single scan of MRI data (400 data points in total). Using SPM software, voxel-based general linear model analyses were performed in the whole brain to find regions correlated with spontaneous fluctuations of mu rhythm power physically at rest. We found that greater BOLD activities in the IPL and PMv were linked with suppression of mu rhythm power. Furthermore, we discovered that the functional connectivity between IPL and PMv was decreased when the power of mu rhythms was suppressed. We did not find any brain regions showing greater activities or functional connectivity in association with increases of mu rhythm power. We conclude that greater activity but reduced functional connectivity of IPL and PMv are correlated with spontaneous suppression of mu rhythm amplitudes at rest. Our results may provide new insight into mechanisms of spontaneous fluctuations of brain activity or connectivity in a resting state. P185 Investigation of the neural correlates of tool use with activation studies in healthy subjects and lesion studies in brain damaged patients E. Salazar-Lopez1, M.L. Brandi1, G. Goldenberg2, A. Wohlschlaeger3, L. Johannsen1, J. Hermsdoerfer1 1Technische Universitaet Muenchen, Lehrstuhl fuer Bewegungswissenschaft, Muenchen, Germany; 2Klinikum Bogenhausen, Klinik fuer Neuropsychologie, Muenchen, Germany; 3Technische Universitaet Muenchen, Klinikum rechts der Isar, Diagnostische und Interventionelle Neuroradiologie. Neuro-Kopf-Zentrum, Muenchen, Germany Question: Results from brain activation studies in healthy subjects and lesion analyses in brain damage patients are expected to reveal a correspondence between areas activated by task performance with lesioned areas in case of deficits. We are planning to directly compare both approaches to study the neural network of tool use in as similar as possible and as realistic as possible conditions: On the other hand we examined tool use in healthy elderly subjects, during the realization of fMRI. On the other hand we plan to correlate the execution in this task in chronic stroke patients – with apraxia – with their damaged brain areas. Methods: Both experiments used a tool carousel for controlled tool presentation (12 tools of daily life). The fMRI-data was analyzed with SPM8 in a factorial design (object and task) during the planningand action-phase. In the lesion analyze study we score the execution according to an apraxic errors scale and use the voxel based lesion symptom mapping (VLSM), a method that includes mapping the lesion manually, normalizing brain image using cost function masking with SPM8 and making a voxelwise statistical analysis of neurological lesions to define the relationship between tissue damaged and behavior. Results: Besides a clear left-sided lateralization, a wide spread network can be identified with the fMRI analysis (see figure). This is specific to planning tool use and includes parietal cortex (superior and inferior parietal lobule and intraparietal sulcus), frontal cortex (dorsal and ventral premotor cortex

Safety of EEG–fMRI recordings in newborn infants at 3T: A study using a baby-size phantom

ObjectiveWe aimed to study EEG electrode temperatures during MRI recordings using a neonatal-size phantom to establish the safety of neonatal EEG–MRI. MethodsWe constructed a phantom set-up for co-registration of EEG and MRI measurements with newborn size configurations. The set-up consisted of a spherical glass phantom fitted with a customised MRI-compatible 64-channel EEG cap and EEG amplifier. Temperatures were recorded during and after five different scanning sequences (two T2∗ sensitised BOLD fMRI, one T1-weighted and two T2-weighted spin echo) in five electrode locations using a thermistor that was integrated into the electrode housing. A temperature increase >4°C was defined a priori as the safety limit. ResultsDuring fMRI and T1 sequences, none of the electrodes showed meaningful temperature changes. Only one MRI sequence (T2 with Max turbo factor 25; SAR 89%) caused temperature increase in one electrode (Fpz; +4.1°C) that slightly exceeded our predefined safety limit, while the conventional T2 sequence was within safety limits (up to +1.7°C). ConclusionsCo-registration of EEG and fMRI can be considered safe in babies with respect to electrode heating, which is the primary safety concern. SignificanceThe present findings open up a possibility to commence studies where EEG and MRI/fMRI are co-registered in human babies. Such studies hold significant promise of a better understanding of the early development of brain function and neurovascular coupling.

The relationship between the localization of the generalized spike and wave discharge generators and the response to valproate

Up to 30% of patients with idiopathic generalized epilepsy (IGE) have seizures that are refractory to medication despite appropriate therapy that commonly includes valproate (VPA). The aim of this study was to compare patients with VPA-refractory and VPA-responsive IGE in order to determine whether there are group differences in generalized spike and wave discharge (GSWD) generators that may be associated with VPA resistance. Of 89 IGE patients who underwent electroencephalography (EEG) combined with functional magnetic resonance imaging (fMRI; EEG/fMRI), 25 with GSWDs identified in EEG/fMRI data were included. Simultaneous acquisition of 64 channels of EEG data at 10 kHz was performed using an MRI-compatible EEG cap and amplifier at 4T. VPA resistance was defined as lack of seizure control despite therapeutic dose of VPA. The fMRI blood oxygen-level dependent (BOLD) correlates of GSWD in the entire group involved midline thalamus, frontal regions comprising Brodmann areas 6, 24, and 32, and temporal lobes diffusely. When VPA-responsive and VPA-resistant patients were compared, BOLD signal increases were noted in the VPA-resistant patients in medial frontal cortex, along the paracingulate gyrus (Montreal Neurological Institute; MNI x = 2, y = 13.6, z = 45.9), and anterior insula bilaterally (right MNI x = 37.6, y = 7.8, z = 0.6, left MNI x = -35.3, y = 13.6, z = -5.3). Our findings support the hypothesis that VPA-resistant and VPA-responsive patients may have different GSWD generators. Furthermore, we hypothesize that these differences in GSWD generators may be the reason for different responses to VPA.

Usefulness of a 1.5 T MRI-compatible EEG electrode system for routine use in the intensive care unit of a tertiary care hospital

Continuous electroencephalogram (cEEG) recordings are being increasingly used in intensive care units (ICUs) to detect epileptic seizures and other changes. MRI scans can interrupt such recordings if the EEG electrodes need to be removed and important data can be missed. We retrospectively examined EEG recordings from ICU patients who underwent MRI scans, comparing those from patients with the MRI-compatible EEG electrodes with those who had to have the EEG electrodes removed before scanning. We also examined technical aspects of the recording and scalp abrasions in both groups. Fourteen of 31 (45%) EEG recordings with the MRI-compatible electrode system in patients that underwent MRI scans between 03:00 p.m. and 07:00 a.m. (when technologists were not available) captured seizures. In contrast, all of the six EEG recordings with the MRI-incompatible electrode system in patients that underwent MRI scanning during the same interval were interrupted and had no data. Recording characteristics of the EEGs were comparable between the two groups and none had scalp abrasions. A significant proportion of patients undergoing MRI scans with the MRI-compatible EEG electrodes had seizures that would have been missed if the MRI-incompatible EEG electrodes had been used.

Trial-by-trial analysis of combined EEG and fMRI shows dynamics of cognitive function

Event Abstract Back to Event Trial-by-trial analysis of combined EEG and fMRI shows dynamics of cognitive function Ana Diukova1*, P. Mallikarjun1, D.P Auer1 and P.F Liddle1 1 University of Nottingham, United Kingdom Introduction: While most of the studies analysed responses to visual stimuli [1] and the error-related negativity [3] & [2], we report reliable recording and results of the trial-by-trial analysis of the auditory ERP in spite of the noisy MR environment. Further application in auditory ERP research includes comparison between healthy controls and patients with psychosis. Methods: Simultaneous recording of EEG/fMRI was applied to identify BOLD changes associated with target detection task. Twenty healthy volunteers participated in the study. Paradigm and study design: Continuous EEG and whole-brain fMRI recordings were made while the participants were required to press a button for infrequent target stimuli and ignore frequent non-target stimuli. Stimuli were presented randomly (Target/Standard Tone=15%/85%; ISI=3 sec). EEG Recording: EEG data were recorded using the MRI compatible BrainAmpMR EEG amplifier and the BrainCap electrode cap with 30 sintered Ag/AgCl ring electrodes, sampling rate was 5000 Hz. fMRI Acquisition. fMRI was performed using a Philips 3T MRI scanner (TE/TR=35/2100ms, matrix 64x64, voxel size 3.25x3.25x3 mm, 35 slices). Data Analysis: EEG data was analysed using Brain Vision Analyzer software and EEGLAB 5.03. Extended infomax ICA was performed on the MR-denoised single subject continuous EEG data. Then data was epoched across the target stimuli. The 31 ICs for each subject were screened for maps resembling the typical ERP topography, the time-frequency distribution was plotted and the appropriate IC was chosen. The resulting single-trial IC ERP amplitude vector was used as a parametric modulation for MRI design matrix. The fMRI data was realigned, normalised and spatially smoothed with 8 mm Gaussian kernel, using SPM2. The design matrix was generated using synthetic HRF and its first derivative. The design matrix consisted of an onset vector of target stimuli, IC ERP amplitude vector as a parametric regressor and six rigid-body motion correction parameters entered as confounding covariates. Results: At the group level (n=20), the amplitude of single trial IC ERP co-varied with BOLD response within the frontal and parietal cortex, cingulate gyrus, thalamus, cerebellum, posterior temporal lobe and insula (Figure). These findings confirm previous fMRI evidence of widespread cerebral activity during performance of auditory oddball task, and furthermore demonstrate that the BOLD activation is correlated with EEG activity. tn_pic1 pic1

MRI compatible EEG electrode system for routine use in the epilepsy monitoring unit and intensive care unit

MRI compatible EEG electrode system for routine use in the epilepsy monitoring unit and intensive care unit