[Eeglablist] OPen software for ONLINE filtering EEG-fMRI

[Makoto Miyakoshi]

Dear Agustin,

David is absolutely right. Gradient artifact needs to be subtracted from
the channel signal to recover underlying EEG signal. The gradient artifact
template is usually built by using multiple repetitions of the artifact
itself. The waveform of the gradient artifact is determined by spatial
location of the electrode and cables inside the scanner, so virtually there
is no way to predict it beforehand. The simplest method to build such a
template is to calculate event-related potential of the gradient artifact.
This works only when the artifact is perfectly stationary, which is usually
impossible due to subject's movement. There are various signal processing
approaches, but there is no perfect solution for this.

Even if you are lucky enough to subtract gradient artifact well, you still
need to do pretty much the same for ballistocardiogram which has lower
amplitude than the gradient artifact but probably more tricky.

If you have a good calibration period from which you can build a nice
template for both GA and BCG, AND an ideal subject who does not move at all
(total <1mm across xyz throughout the scanning), online solution would
work. After all, the difficulty here is subject's body movement inside the
scanner. If your subject is an animal with its skull fixed to the base,
such an online processing would work.

Makoto

On Mon, Sep 3, 2018 at 2:21 PM Agustín Solano <asolano at bioingenieria.edu.ar>
wrote:

> Hi everybody. Does anyone know any open software for ONLINE removing
> gradient artifact in EEG during EEG-fMRI acquisition?
> I think it like an alternative for the RecView software of Brain Products
> MR amplifiers.
>
> Thanks!
>
> --
> *Bioing. Agustín Solano*
> Instituto de Fisiología y Biofísica (IFIBIO) - Bernardo Houssay
> Laboratorio de Fisiología de la Acción, Facultad de Medicina (UBA)
> Paraguay 2155, Capital Federal
> Buenos Aires, C1121ABG
> Argentina
> Tel: 54 11 5 950 9500 (2132)
> http://www.physiologyofactionlab.info
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-- 
Makoto Miyakoshi
Swartz Center for Computational Neuroscience
Institute for Neural Computation, University of California San Diego
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