Hi,
So - I wrote mni2tal and...
> I have used two functions to convert SPM coordinates for Talairach usage.
>
> 1. mni2tal.m (from Matthew Brett)
>
> 2. icbm_spm2tal.m.
>
> The two give quite different results (sometimes differing some mm).
> Should I take in consideration only the second one (said to be more
> precise)? Or is there another tool even more precise?
I think the answer is fairly simple.
Case 1) If you want to match your MNI normalized brain, to a template
of normal brains that has been Talairach transformed (the rather odd
piecemeal linear transform used by Talairach), then the icbm_spm2tal
transform is the way to go.
Case 2) If you want to match to the Talairach atlas brain, the
icbm_spm2tal transform will give you some wrong results, and I would
use another transform. If you look here:
https://cirl.berkeley.edu/mb312/icbm_transform/
you will see a set of png images showing the relationship between the
MNI template, the downloaded Talairach daemon brain, the MNI template
transformed with the icbm_spm2tal transform, and the MNI brain
transformed with the mni2tal transform. You'll see that the
icbm_spm2tal transform tips up the MNI atlas, making the match in the
orbitofrontal and lateral temporal regions worse. The reason for
this is probably that the Talairach transform does not do a good job
of matching to the very odd shape of the Talairach atlas brain.
So, personally, I would definitely use the icbm_spm2tal transform in
case 1), but not case 2). If you want a case 2) transform, I believe
the transform implemented in BioimageSuite is particularly good, but
mni2tal is still better than nothing.
Best,
Matthew
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