Dear Stephen,
I think, there are not much other things to do, except throwing away that data set, which of course would be the most reasonable thing to do, but sometime, you can do that; in rare single cases, for example.
In that case, I would do (have done) exactly the same thing.
Karsten
"Stephen J. Fromm" <[log in to unmask]> schrieb am 09.11.05 14:29:28:
>
> I was wondering if anyone would care to comment on a method for dealing
> with isolated bad volumes in data. An example would be a volume that's
> rendered unusable because of movement during the volume. (Leads to
> alternating slice brightness.)
>
> One cannot merely discard the entire timepoint, because that would lead to
> a discontinuity in the time series.
>
> For the statistics itself, I add a "user-specified" regressor singling out
> that individual timepoint, to "regress out" the effects of that volume.
>
> At the preprocessing stage, the volume must be replaced if slice timing
> correction is used, else the data corruption will "spread" in time.
> Currently I merely replace the volume with the average of the neighboring
> volumes.
--
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Karsten Specht, PhD
Department of Biological and Medical Psychology
& National Competence Centre for functional MRI
University of Bergen
Jonas Lies vei 91
5009 Bergen
Norway
Tel.: +47-555-86279
Fax: +47-555-89872
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http://fmri.uib.no/
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