Thank you Larry,

You answer most of my doubts, the comments were very helpful.

I left them coregistered to the MNI space and this solved the problem with rotation while importing into SPM.

The problem now is how to define a center to these images in SPM. At this point, an analysis would generate valid results (even without centering the images)? I suspect the answer is no, and in this case how could someone center them at the posterior comissure, since these images are diffs that were smoothed during the process of ISAS analysis, hindering the recognition of anatomical landmarks?


Best,

Luis