afni.nimh.nih.gov

If your dataset is specifically in TT_N27 space (you have aligned all your data to the TT_N27+tlrc template, then you can use the exact transformation, the inverse of the 12-piece transformation that brought the N27 dataset to Talairach space. This command applies that inverse transformation:

3dfractionize -input dset+tlrc -warp ~/abin/TT_N27+tlrc -prefix dset_mni -template template_mni+tlrc