Hi
On 23 Oct 2008, at 06:31, Anthony Ang wrote:
> Hi,
>
> When I layer the mask MNI-maxprob-thr0-1mm mask from the FSL MNI
> Atlas onto the MNI152_T1_1mm_brain, the mask appears larger than
> the brain.
> Why is this so?
Because the MNI152 is derived from a mixture of Americans and
Canadians, whereas the probability masks are just Canadians, who have
larger brains.
Oh, my wife tells me that's not the case, so it must be: the
MNI152_T1_1mm_brain is the result of averaging together many brains,
and so reflects the average size, whereas the MNI-maxprob-thr0-1mm by
definition is the multiple-subject atlas data thresholded at "thr0" -
so by definition it will reflect the largest brains used for the
atlas, not the average. You can ignore the extra voxels if you're only
interested in results inside the average brain.
> Can I crop away the excess mask (not covering the brain)?
Yes.
Cheers.
> I am creating masks of the temporal lobe, parietal lobe and so on
> from MNI-maxprob-thr0-1mm file. I find that after registering the
> temporal lobe mask to the subject brain, the registered temporal
> lobe is actually larger than what you would expect (extend beyond
> the brain).
>
> Thanks.
>
> Best regards
> Anthony
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Stephen M. Smith, Professor of Biomedical Engineering
Associate Director, Oxford University FMRIB Centre
FMRIB, JR Hospital, Headington, Oxford OX3 9DU, UK
+44 (0) 1865 222726 (fax 222717)
[log in to unmask] http://www.fmrib.ox.ac.uk/~steve
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