Hi - it depends how the artefact is interacting with the signal of
interest. If it's very strong then if may be best to ignore that
timepoint completely, in which case you could add an extra regressor
into FEAT that is zero at all timepoints except when the spike occurs.
Cheers.
On 9 Jun 2009, at 16:02, Emma Liang wrote:
> Dear Dr Smith,
>
> Thanks a lot. The ICA paper is very helpful. But I am a very beginer
> on signal processing methods, still need time to digest it. My
> current comprehension is that each MELODIC component is a part of
> original signal throughout the whole time serial. In my data, the
> scanner 'spike' noises affected each component and made the real
> activation signal very insignificant. I want to filter the EPI
> imaging by cutting all the intensity over 1000(machine spikes at
> over 2000) to 1000 and make them as a task. Is it ok? and is there a
> function to do that? Sorry if the question is too silly.
>
> Cheers,
> Emma
>
> On Fri, Jun 5, 2009 at 4:07 PM, Steve Smith <[log in to unmask]>
> wrote:
> Hi, see the FAQ:
>
> http://www.fmrib.ox.ac.uk/fslfaq/#melodic_filter
>
> Cheers.
>
>
>
> On 3 Jun 2009, at 12:42, Emma Liang wrote:
>
> Dear FSLers,
>
> I have a EPI imaging with some white noise slices throughout(about
> 20 of 500 volumes contaminated) because a unknown scanner fault. Is
> there any method to get rid of them or ignore? I'm going to make all
> the volumes with noise as a separated task, is it feasible?
> Thanks!
>
> Cheers,
> Emma
>
>
> ---------------------------------------------------------------------------
> Stephen M. Smith, Professor of Biomedical Engineering
> Associate Director, Oxford University FMRIB Centre
>
> FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK
> +44 (0) 1865 222726 (fax 222717)
> [log in to unmask] http://www.fmrib.ox.ac.uk/~steve
> ---------------------------------------------------------------------------
>
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Stephen M. Smith, Professor of Biomedical Engineering
Associate Director, Oxford University FMRIB Centre
FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK
+44 (0) 1865 222726 (fax 222717)
[log in to unmask] http://www.fmrib.ox.ac.uk/~steve
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