Hi Bernard,
>
> The voxel size of the raw imagies (1.02x1.02x1.2)or (0.93x0.93x2.5)is
> different, I am wondering if I can compare them after the
> pre_processingsteps?
After pre-processing (normalisation) they will all have the same voxel size, and can IN PRINCIPLE be compared. However, if you are talking VBM you will have different influences from partial volume effects, if your are talking fMRI you will have slightly different resolution that may or may not "matter" depending in what filter width you use for your smoothing.
My gut feeling is that you would still be OK as long as the voxel-difference is NOT colinear with any effect of interest in your study, for example as long as not all controls were scanned with one size and all "sick ones" with another size.
Good luck Jesper
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