David, with respect to the idea of "internal standard", I suggested to a
colleague doing DTI on the neonates to run a seed classification of thalamus
(Tim has done in his Nature paper) in order to obtain a subregion of the
thalamus, and run tracking from this subregion to its corresponding target.
Unfortunately, the data she has from the babies are not of the greatest
quality. What do you think about the idea?
Martin
On Friday 05 December 2008 02:08:58 David Gutman wrote:
> Cherif I have noted similar absolute number differences between
> subjects, like a scaling difference, where the tracts themselves look
> extremely similar. My current thoughts are that the "trackability" of
> an image varies significantly from subject to subject depending on
> things like you mentioned, scan quality, motion, etc...
>
>
> One thing I was thinking of, almost analogous to other methodologies
> (like when you try and amplify DNA/RNA you may choose a gene that
> "shouldn't be different" to serve as a loading control and use that to
> scale all of your values... myosin or actin or other messenger genes
> are often used in this sort of analysis, and the relative
> mRNA/whatever expression is correlated using some sort of internal
> standard....
>
> For DTI, I am unaware of any "internal standard"/tract that could be
> used for comparison, and have played around with this in the past
> (although it's been a while). I'd really like to get other people's
> feedback on this concept; in particular it would be nice to pick a
> relatively uninteresting region (or combination of regions) where you
> say calculate the number of fibers along the optic radiations, or
> maybe part of the corpus collosum and for every subject tract the
> number of fibers that make it from A to B and then use this reference
> tract to scale all of your more "interesting" tracts.... so basically
> pick a region that you think should not change between
> people/subjects/whatever...
>
> Also just looking at relative percentages instead of absolute numbers
> may get around this sort of issue of just looking at raw numbers which
> is often what I wind up doing (although this also can have its
> pitfalls).
>
>
> DG
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