Hi, MELODIC-based cleanup takes a component that you have selected,
and 'multiplies' the component's timecourse by its spatial map, to
produce a 4D dataset (of the same dimensions as your original data)
that represents the artefact you selected. This is then simply
subtracted out of the original data.
Cheers, Steve.
On 11 Feb 2008, at 19:05, Shawn Yeh wrote:
> Dear FSL users,
>
> I am currently looking into using MELODIC to identify and filter out
> excessive motion that cannot be adequately compensated by McFLIRT.
> The FSL
> website explains how to use Melodic, but I am having a hard time
> finding out
> how the filtering works. My questions:
>
> Does it average, smooth, or interpolate out the respective voxels with
> respect to the component time courses(as generated by melodic), or
> simply
> reduce/increase the voxel intensity by the thresholded amount?
>
> In theory, doesn't including the motion estimates as separate ev's
> already
> attempt to 'devalue' these voxels associated with motion?
>
> Since the IC's usually have a periodic aspect to their model, how much
> non-motion voxel changes are being filtered out? I understand
> 'rimming'
> effects are effectively removed this way, but I am looking at some
> interleaving effects from motion that doesn't look as safe to filter
> out.
>
>
> Help on this topic greatly appreciated, thanks in advance,
> Shawn
>
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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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