| When i am realigning my data i get an error saying there is not enough
| overlap to realign the data and to check that the hdr is OK! What could
| this mean? I used check reg to look at the images by hand and they looked
| fine to me.
Realignment involves moving one image around so that the sum of squares
difference between it and the reference image is minimised. If the
image is moved too far, then there are not enough common voxels for this
to work properly, and the registration fails. This can happen if there
are not many slices in the images and/or the subject moves a lot.
If this is not the case, then it may be worth checking out the realignment
defaults. There is an option in there that makes a tradeoff between speed
and accuracy. Try selecting a more accurate setting, which may prove to
be more robust.
The warning about checking headers/mat files is to make sure that the origins
and orientations of the images have not been set so that the brains are
a long way apart.
Best regards,
-John
|