Dear Glenn:
It's a little odd that if your structurals don't have signal loss, and
you're applying the normalizatiopn parameter set of your structurals to
your functionals that you get this problem. Perhaps the result looks odd
since you're normalizing wisps of brain. In any case to reduce this you can
1) only use affine normalization
2) reduce the number of non-linear basis functions so that the brain is not
being stretched as much.
or
3) adjust your 3T sequence to reduce blow-out (i.e. thinner slices and
other measures).
Regards,
Darren
At 09:58 PM 11/9/2001 +0000, you wrote:
>Hello all,
>
>We've recently run into a problem using SPM to normalize functional scans
>acquired on our 3T magnet. Because it's a 3T, we get 'blow-out' of
>orbital, frontal cortex due to the nasal sinuses. This means that the
>brains we acquire have a peculiar shape (no orbital cortex). When we go to
>normalize these, SPM warps them into standard space -- but SPM doesn't know
>that they have no orbital cortex. This results in distortions: much of
>the brain is dragged anterior and inferior to where it really should be.
>
>The stuctural scans are not affected in the same way, and they normalize
>correctly. However, applying the parameters determined by normalizing the
>structurals to the functionals results in much the same problem.
>
>Does anyone have any fixes for this sort of problem?
>
>Many thanks,
>
>Glenn Wylie.
Darren R. Gitelman
Northwestern University, Evanston, IL. USA
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