The option in Dartel for computing Jacobian determinants is only
intended to do it from the Dartel velocity fields. It won't work for
other representations of deformations.
There are routines within SPM for computing Jacobian determinants, but
they do not have a nice user interface included with them. For
example, the spm_def2det function in the HDW toolbox could be used
(although it does not have any associated documentation).
What exactly do you hope to do with the Jacobians? If you want to do
some form of TBM-like analysis, I certainly would not suggest using
the sn.mat files.
Best regards,
-John
On 7 February 2012 16:45, Fabrizio Pizzagalli
<[log in to unmask]> wrote:
> Dear SPM's users,
>
> I would like to compute the Jacobian of the normalisation fields in SPM8.
>
> From the _sn.mat I obtain the deformation fields using the util "Deformation". Then I compute the Jacobian with the DARTEL tool "Jacobain determinants" but the results are not satisfactory.
>
> Could you tell me if I have made some mistake and how I can compute the Jacobian starting from the _sn.mat parameters?
>
> Thanks in advance,
> Fabrizio Pizzagalli
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