[MINC-users] global t-test

[Sylvain MILOT]

Hello Anil,

I haven't dealt with this kind of data personnally but you may want to have a look
here:

http://wiki.bic.mni.mcgill.ca/index.php/FullTextSearch?s=vbm

I don't know how up-to-date this is but I'm pretty certain you should find what you're
looking for!

Now concerning glim_image, it should be feasible to use it to do exactly what you want.
I doubt you should use the pooled sd measure since it requires that the sd image be
stationary. Using the voxel sd measure would be more appropriate.

It should also be possible to use Keith Worsley's latest method via fmristat's
multistat script which regularizes the random effects variance by smoothing the ratio of
fixed+random/fixed effects SD volumes and multiplying back by the fixed effects SD. Keith calls
this a form of local sd pooling. Look here for references http://www.math.mcgill.ca/keith/.
If it can be tailored to PET data, it should be feasible to taylor it to VBM data. I'm pretty sure
Jason Lerch has already done this and maybe he'll answer your call when he
gets a chance. In the meantime look at the wiki!

Hope this helps a little,

Sylvain



On Tue, 6 Dec 2005, Anil Ashok Kuchinad, Mr wrote:

> Hello,
>
>
>
> I am running a VBM analysis and I wanted to obtain on statistic that I
> am not sure how to find. I was curious if someone knew what command
> would allow me to find an overall t-value for the comparison between all
> grey matter voxel density in one group vs. another. I basically want to
> find the overall difference in grey matter density across the whole
> brain between two groups.
>
>
>
> I am aware that glim_image has a pooled function but I couldn't get it
> to work for me. I am truly shooting in the dark whether I am to use
> glim_image and then run something similar to find_peaks or
> tstat_threshold later on.
>
>
>
> Hopefully this is possible!
>
>
>
> Anil
>
>
>
>
>
> ----------------------------------------------------
>
> Anil Kuchinad
>
> Centre for Research on Pain
>
> McGill University
>
> Strathcona Anatomy and Dentistry Building
>
> 3640 University St., Room M/19
>
> Montreal, Quebec , Canada
>
> H3A 2B2
>
> Tel: (514) 398-1271
>
> Email: anil.kuchinad at mcgill.ca
>
>
>
> _______________________________________________
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>

---
Sylvain Milot (sylvain at bic.mni.mcgill.ca)
              (trinity at bic.mni.mcgill.ca)
Brain Imaging Centre
Montreal Neurological Institute
Webster 2B, Room 208
Montreal, Qc., Canada, H3A 2B4
Phone  : (514) 398-4965, Fax: 398-8948
Mobile : (514) 712-1768
Office : 527 Av Des Pins O., Room 204
         Montreal, Qc., H2W 1S4