I am using ART (3dwarper) to register a patient image to the MNI152 standard. I would like to compute the inverse transform, and my understanding is that I can use ivf for that (taking original dim, pixdim into account). However, when I use 3dwarper with the -A and -acpc options it computes it's own initial affine transformations. So, if i simply apply the inverse warp to the MNI152 standard, to bring this image to my patient space, do I not still need to apply an inverse affine transformation? Could someone help me figure out how to do this with the ART tools?

Apologies for the rough syntax, here are my steps:

1. register patient.nii to mni152.nii with 3dwarper, using -A -acpc options: output is warp.nii
2. compute inverse warp using ivf: output is inverse_warp.nii (yes, I account for dimensions of the original image)
3. apply inverse_warp.nii to mni152.nii using applywarp3d: output is mni152_2_patient.nii,  **but what is the initial affine and/or rigid body transform I should be passing to applywarp3d?**

Thank you very much in advance!

Paxton