I haven't encountered this problem before, but it seems very strange.
When you say that the u_*.nii files are empty, do you mean that all
the values are zero, or all values are not finite (NaN or Inf)? This
could give some clues.
Note that when you re-run the code, Dartel will use starting estimates
from existing u_*.nii. Therefore, it could be an idea to delete the
u_*.nii before trying again.
Also, Dartel is quite verbose in terms of what it prints out in the
MATLAB window. Perhaps there are some clues among that lot.
The thing that most concerns me are the failures, for which I don't
have a good explanation. The fact that your template is not the
average of the entire population in your study may not be an extremely
major issue. For many years, SPM used the single subject MNI brain as
a template for spatial normalisation.
Best regards,
-John
On 15 March 2012 13:19, Philipp Baumann <[log in to unmask]> wrote:
> Dear SPM'rs,
> I'm doing some VBM analysis with the latest SPM8, on a macbook Pro, matlab student version.
> When I run DARTEL (create template), I get a template_6.nii file which is fine. However, some of the u_r1.nii files are "empty" with no intensity at all while some are good. I'v checked all rc1 and rc2 files which seem ok (the T1 images look all good). I tried to run this twice with the same problem. I don't get any error message.
>
> I then tried to run DARTEL (existing template) to realine the subjects that did not work with the first DARTEL step. This worked well and I could generate the missing flow fields. I guess not all the subjects were used to create the template and I obviously this is not really acceptable.
>
> What may have gone wrong with my initial DARTEL (create template) step ? Any ideas ? I'm a bit stuck with this issue. There might be an obvious mistake that I missed.
>
> Thank you very much,
>
> Best regards,
>
> Philipp
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