The "pushing" procedure is just for the normalise to MNI space option
of Dartel. The "pulling" procedure uses the inverse of the
deformation and involves scanning through the new image, filling in
each voxel by sampling the appropriate location in the original image.
"Pushing" involves scanning through the original image and adding in
the values to the appropriate place in the new image.
For Jacobian scaled ("modulated") data, the pulling operation would be
followed by rescaling by the Jacobian determinants of the deformation,
whereas this is not needed for the "pushing" as the original values
are preserved exactly.
For unscaled ("unmodulated") data, the pushing operation would be
followed by dividing through by a count of the number of original
voxels that are added to each location of the new image.
Best regards,
-John
On 17 December 2010 10:13, Tetiana Dadakova <[log in to unmask]> wrote:
> Dear SPM list,
>
> I am trying to understand if there is any difference in normalization
> procedure in SPM5 vs SPM8.
>
> In the manual to SPM8 it is written that "Normalised images are
> generated by a “pushing” rather than a “pulling” (the usual)
> procedure". Could someone please explain me what does this mean?
>
> Thank you in advance,
> Tetiana.
>
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