> We have one more question on VBM. Prior to generation of parametric maps we
> have calculated grey, white, CSF volumes and fractional volumes using a
> script provided by John Ashburner (thank you John, it works great!!)
>
> We have calculated the fractional volumes on non-normalized sergmented
> images using the optimized Good's technique on a group of patients and
> controls.
>
> Is it correct or should we calculate the brain volumes on NORMALIZED and
> segmented images??
>
> We have tried both and the fractional volumes significantly differ...
Have you appled the volume preservation step using the spm_preserve_volume.m
script that I think I sent to the list a while ago? This should modify the intensities in
the segmented normalised images such that the amount of grey matter is preserved.
If you have applied this script, then the answers should be similar.
Best regards,
-John
--
Dr John Ashburner.
Functional Imaging Lab., 12 Queen Square, London WC1N 3BG, UK.
tel: +44 (0)20 78337491 or +44 (0)20 78373611 x4381
fax: +44 (0)20 78131420 http://www.fil.ion.ucl.ac.uk/~john
|