Dear Stefano,

The difficulty here is identifying exactly what the location and extent of the
hypothalamus ROI should be.  You are right that you cannot use FIRST.
You could use a registration-based method (single or multiple atlas method)
but I'm not sure how you could use VBM without separately defining the ROI.
Manual delineation is also an option of course.

I would not have added the FIRST volumes to your VBM analysis, as this is
not correcting for multiple comparisons but looking for separate, uncorrelated
variation.  As you might expect different structures to vary in volume in a
systematic way (e.g. with head size or disease duration) then I would not 
expect uncorrelated changes.  

If you want to make sure that your final results are corrected for multiple
comparisons (due to the multiple structures being considered) then you
should apply a Bonferroni correction to the set of p-values that you obtain.

If you are just looking at volume changes then I think it is fine to put in
your hypothalamus results in with the changes from FIRST.  There should
not be any bias in the different within-structure results and so I don't think
there is any need to do anything special.  The big problem is just getting a
good method for defining the hypothalamus ROI.

All the best,
	Mark





On 2 Apr 2012, at 17:45, Stefano DP wrote:

> Hi list,
> I have performed a volumetric analysis of subcortical GM using FIRST tool. In addition, I need to include the hypothalamus assessment. Because hypothalamic segmentation is not included in FIRST package, I have separately performed a ROI-VBM analysis on hypothalamus. ROI of the each seven FIRST segmented volumes were also added in VBM analysis to correct hypothalamic results for multiple comparison.
> What is your opinion about these steps? 
> Is possible to get from the ROI-VBM, the volume of the hypothalamus for each subject?
> What do I do to avoid that hypothalamic results can be treated separately from the rest of the subcortical GM volumes?
> Many thanks in advance.
> Regards,
> 
> Stefano Delli Pizzi
> University of Chieti
>