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Ballistocardiographic artifact removal from simultaneous EEG-fMRI using an optical motion-tracking system
Pierre LeVan1, Julian Maclaren2, Michael Herbst1
1Dept. of Radiology, Medical Physics, University Medical Center Freiburg, Freiburg, Germany.
Neuroimage
|March 8, 2013
Summary
This study introduces an optical motion-tracking system to reduce ballistocardiographic (BCG) artifacts in simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI). The new method significantly improves EEG quality during MRI scans.
Area of Science:
- Neuroimaging
- Biomedical Engineering
- Signal Processing
Background:
- Simultaneous electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) offer high temporal and spatial resolution for studying brain activity.
- Ballistocardiographic (BCG) artifacts, caused by cardiac-related motion, significantly degrade EEG quality within MRI scanners.
- Standard artifact removal methods like average artifact subtraction (AAS) struggle with BCG variability.
Purpose of the Study:
- To investigate the efficacy of an optical motion-tracking system for directly measuring BCG motion.
- To assess the potential of motion parameter regression for reducing BCG artifacts in simultaneous EEG-fMRI.
- To compare the performance of the novel method against standard AAS techniques.
Main Methods:
- Developed and implemented an optical motion-tracking system to record BCG-induced motion.
- Applied linear and quadratic regression of motion parameters to remove BCG artifacts from EEG data.
- Compared artifact reduction efficacy with standard AAS and sequential regression-AAS approaches.
- Evaluated results using root-mean-square (RMS) amplitude reduction and comparison with reference EEG data.
Main Results:
- The optical motion-tracking system accurately measured BCG motion in human subjects.
- Regression of motion parameters significantly reduced BCG artifact RMS amplitudes compared to AAS (p<0.05).
- Sequential application of regression and AAS yielded further significant RMS reduction, approaching the quality of EEG recorded outside the scanner.
- Analysis indicated that non-rigid motion of EEG wires, stemming from head motion, significantly contributes to BCG artifacts.
Conclusions:
- Optical motion tracking combined with regression offers a superior method for removing BCG artifacts in simultaneous EEG-fMRI compared to AAS.
- The findings highlight the importance of considering non-rigid wire motion in artifact reduction strategies.
- This approach enhances the quality of EEG data acquired during fMRI, improving the reliability of combined neuroimaging studies.
