Hi Ashley -
There's a little bit of discussion of using a single template versus
using two group-specific templates for TBM here
(and why they'd give different results):
http://www.loni.ucla.edu/~thompson/ADpapers.html
- please see the Discussion and Figure 1 in paper #7 there (X. Hua et
al., 2008). I think it makes sense
to compute your Jacobian maps within subject first, and then transfer
them all onto the same template.
I hope this helps!
Paul
Paul Thompson
Professor of Neurology
Lab of Neuro Imaging
UCLA School of Medicine, Los Angeles, CA 90095, USA
http://www.loni.ucla.edu/~thompson/thompson.html
On Jul 28, 2008, at 12:08 PM, Ashley Conway wrote:
> We are looking for anatomical changes in young women at two points
> of the menstrual
> cycle. We have T1 structural images from each woman (n=14) at both
> time points (each
> woman was scanned twice approximately 2-weeks apart). Although our
> design is similar
> to a longitudinal within-subjects design, I haven't found a posting
> specific to our situation
> where the time points are commutative. I'm wondering if that
> matters, and what the best
> approach would be.
>
> We are using optimized VBM in SPM2 for processing, and using a
> paired-t statisical design
> to compare gray matter volumes between the two points of the cycle.
>
> Initially we performed the analysis using two customized templates
> (one for each group),
> and found several regions with highly significant changes in gray
> matter volume (as well
> as gray matter density, but are unsure of how to interpret those
> findings?). When we
> complete the analysis with a single template comprised of average
> images made from
> the two scans of each woman, our results are not nearly as
> significant. Which approach
> (if either) is valid?
>
> Additionally, if we repeat the analysis in SPM5, would it be better
> to use the standard
> template or create our own, considering our sample is only women?
>
> Also, should we co-register each woman's structual images together?
>
> Thanks in advance for any advice and guidance,
> Ashley
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