Dear Gilberto,
Oh, that's surprising - the vast majority of studies have a T1-weighted
image, or one very like it (e.g. MPRAGE, etc.).
If you really don't have one then there are two alternatives that you
could try. One is an atlas-based approach where you do non-linear
registration of your image to an atlas and then transfer an atlas
segmentation to your image. You can use the atlases in MNI space
for this, although you'll have to find a FLAIR template in MNI space,
or create an effective one by modifying the intensities appropriately
for the standard MNI image (though this might be difficult).
The other approach would be to try and create a T1-style image
from your FLAIR image. This would require a good segmentation
of the CSF and for you to add together a weighted version of the
FLAIR and the segmented CSF to look more like a T1 image. You
can then run FIRST on this created image and it will hopefully work.
As above, this might be difficult - I don't really know as I'm not very
familiar with processing FLAIR images. It only needs to be a very
good intensity match near the structures of interest in order for this
to work OK, as long as you can get a reasonable initial affine
registration too.
Sorry that there isn't an easy solution, but this is the first time I've
encountered this problem and so we don't have an implemented
solution for it.
Good luck and all the best,
Mark
On 6 May 2011, at 10:29, Gilberto Sousa Alves wrote:
> Thanks for your nice reply, Mark.
>
> Unfortunately, I donīt have any T1 image. Therefore it seems that there is no alternative way to rate hippocampus volume with Flair images, isnīt it?
>
> Cheers,
>
> Gilberto
>
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