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M. Negishi, M. Abildgaard, T. Nixon, R. Todd Constable. Removal of time-varying gradient artifacts from EEG data acquired during continuous fMRI. Clin Neurophysiol, 115(9):2181-2192, 2004.


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Objective: Recording low amplitude electroencephalography (EEG) signals in the face of large gradient artifacts generated by changing functional magnetic resonance imaging (fMRI) magnetic fields continues to be a challenge. We present a new method of removing gradient artifacts with time-varying waveforms, and evaluate it in continuous (non-interleaved) simultaneous EEG-fMRI experiments. Methods: The current method consists of an analog filter, an EEG-fMRI timing error correction algorithm, and a temporal principal component analysis based gradient noise removal algorithm. We conducted a phantom experiment and a visual oddball experiment to evaluate the method. Results: The results from the phantom experiment showed that the current method reduced the number of averaged samples required to obtain high correlation between injected and recovered signals, compared to a conventional average waveform subtraction method with adaptive noise canceling. For the oddball experiment, the results obtained from the two methods were very similar, except that the current method resulted in a higher P300 amplitude when the number of averaged trials was small. Conclusions: The current method enabled us to obtain high quality EEGs in continuous simultaneous EEG-fMRI experiments. Significance: Continuous simultaneous EEG-fMRI acquisition enables efficient use of data acquisition time and better monitoring of rare EEG events


M. Negishi
M. Abildgaard
T. Nixon
R. Todd Constable

BibTex Reference

   Author = {Negishi, M. and Abildgaard, M. and Nixon, T. and Todd Constable, R.},
   Title = {Removal of time-varying gradient artifacts from {EEG} data acquired during continuous f{MRI}},
   Journal = {Clin Neurophysiol},
   Volume = {115},
   Number = {9},
   Pages = {2181--2192},
   Year = {2004}

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