Shift Mask Voxels


I’m noticing that after downsampling my mask it must have rounded up for both left and right hemispheres. The result is that they are both shifted so my mask for my left hemisphere is in the midline of the brain and the mask for the right hemisphere is too far from the midline. Could you please help me with either

a) How to shift the mask over 1 voxel in the L-R direction. Presumably 3dcalc would be good for this but I can’t find the syntax for how this could be approached?
b) Is there a way to alter the way 3dresample rounds so that when I am downsampling I don’t get this problem?

Thank you very much for any help you can provide!



A colleague of mine pointed me to 3drefit to ‘nudge’ the mask.

I used:
3drefit -dxorigin 1x File+orig.

This still doesn’t seem to work the way I expect it to though.
Can anyone help with this?