Dear Freesurfer developers,

I have a dwi.nii image which I want to co-register on a orig.mgz (produced by running recon-all on the subject's T1 image) file without any drop in the quality of image (i.e. without any resolution cost, or changes in the acquired dwi intensity at each voxel). 

I was told that if you just translate the image and don't rotate it during co-registration, the quality of the image won't drop, because you don't cut through the existing voxels on the original image in resampling process to fit it in the destination image. Also, I'm not sure if the --no-resample flag in mri_vol2vol helps with that. 

Can you please guide me toward a better understanding of how co-registration affect the image quality? and ways to prevent that?

Freesurfer version: 7.2 & the Platform in use: CentOS7

Thank you and all the best,

Ela