Hi,
The empty mask image error message happens when a contrast has no
voxels/clusters that survive thresholding. Hence the question here is
why the same contrasts appear to give different results when re-
running poststats. It looks like something has changed (for example,
did you delete the mask image?) between the original run and the re-
run of FEAT. If you're sure that nothing has changed (e.g. you just
ran FEAT from scratch and immediately then tried rerunning poststats
and you still see the problem) then you could upload the original data
and output FEAT directory and we could check - though we'd much rather
debug any problems that are still present in FSL4.1 than in 4.0 - so
if you could upgrade first and see if the problem is still there, that
would be preferable.
Cheers, Steve.
On 9 Oct 2008, at 06:37, Nick Wymbs wrote:
> Hi,
>
> I am having difficulties when I rerun first-level post-stats. This
> happens when I add a couple additional contrasts. Essentially, the
> log file states (1) that I have an 'ERROR:: Empty mask image' or (2)
> I get drastically different stats values. I have replicated the same
> error across platforms, all running fsl 4.0. The error goes away
> when I run the entire analysis over, but my design is quite long and
> I would prefer not having to do this!
>
> Here's an example problem 1:
>
> /Applications/fsl/bin/fslstats thresh_zstat4 -l 0.0001 -R
> ERROR:: Empty mask image
> ERROR:: Empty mask image
> ERROR:: Empty mask image
> ERROR:: Empty mask image
> ERROR:: Empty mask image
> ERROR:: Empty mask image
> 0.000000 0.000000
>
> This is what the log looked like when the contrast was first run:
>
> /Applications/fsl/bin/fslstats thresh_zstat4 -l 0.0001 -R
> 1.644862 3.349561
>
> I believe the problem arises when the contrast manager processes the
> new design.con file. For some reason, the zstat4 file is processed
> as an 'empty' file when valid stats do exist.
>
> I get this:
>
> echo 0 > thresh_zstat4.vol
> zstat4: DLH=0.0101663 VOLUME=0 RESELS=454.153
>
> rather than this (the original):
>
> echo 42375 > thresh_zstat4.vol
> zstat4: DLH=0.0101663 VOLUME=42375 RESELS=454.153
>
> This problem has been noted previously, yet I don't think a
> resolution was reached. See: http://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=ind0801&L=FSL&P=R49090
>
>
> Here's problem 2:
>
> Original:
>
> /Applications/fsl/bin/fslstats thresh_zstat25 -l 0.0001 -R
> 1.645139 39.740047
>
> Error:
>
> /Applications/fsl/bin/fslstats thresh_zstat25 -l 0.0001 -R
> 1.645410 18.897028
>
> Cheers
> Nick
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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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