Miranda,

I'll assume for now that what you mean by 'cluster' is not a cluster in
the sense of clusters produced by a cluster-based correction for
multiple comparisons, which was only very recently introduced to qdec
(actually, just a script generator is produced).  But rather, I think
you mean the areas of significance that remain after you have either
manually adjusted the threshold or just left the thresholds at their
defaults.  If this is what you mean by cluster-size, there is no way now
in qdec to get the size of this 'cluster', outside of drawing a label
around it, and then click on the 'Map Label to Subjects' options, and
looking for the text that says 'Found 389 points in source
label.' (where in this example, the label had 389 points/vertices).

If you want a bit more exact way, you can use tksurfer:

tksurfer fsaverage lh inflated -overlay /path/to/qdec/sig.mgh

to load the sig.mgh file (from your qdec contrast dir of interest), then
adjust the thresholds (View->Configure->Overlay), then click on the
'cluster' you want (the blob), then click the 'Custom Fill' icon (a
paint bucket), then click 'Up to functional values below threshold',
click Fill, and it will fill that 'cluster' and the terminal window will
show you the number of vertices filled.  I'm hoping to add this 'fill'
feature to qdec at some point, to give a label creation option other
than drawing.

Nick




On Tue, 2009-01-13 at 16:43 -0600, nels5...@umn.edu wrote:
> Hello,
> 
> I am wondering if there is an easy way to determine the size of a cluster 
> of significant voxels resulting from a QDEC analysis? I have created a 
> label and mapped the label to all of the subjects, but didn't know if there 
> was a way to extract information about cluster size.
> 
> Thanks,
> 
> Miranda
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> Freesurfer@nmr.mgh.harvard.edu
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> 
> 

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