I am currently trying to register functional EPIs to the subject's anatomical scan while keeping the voxel resolution native. The resulting registered image is cutoff, because the FOVs are different and the COVs are not matched (cf https://fsl.fmrib.ox.ac.uk/fsl/fslwiki/FLIRT/FAQ#Can_I_register_to_an_image_but_use_higher.2BAC8-lower_resolution_.28voxel_size.29.3F).
I am familiar with the solution of adding a translation to the right hand column of the transformation matrix (where the offset to be added should be half of the difference in the respective FOVs). I have indeed tried that (e.g. flirt -in pe1 -out p1_2_anat -ref example_func -applyxfm -init example_func2highres_offset.mat, where example_func2highres_offset.mat is the matrix with the offset added), however, that solution is not working for the dataset I am presently working with (where EPIs are isotropic 2.5mm FOV: 84x84x52; the anatomical is isotropic 1mm FOV 160x256x256), and the resulting registered image is still cutoff.
As a possible alternative approach, I have also created a reference image (using ApplyXFM) that is 2.5mm isotropic (like the functional) with the anatomical's FOV (160x256x256), and used that as "ref" (instead of example_func). Now, while the resulting registered image is not cutoff, it is of course minuscule, and located in the leftmost corner (i.e., necessitating cropping for most visualization etc purposes)...
--Is there a better solution?
Thanks for your help,