Hi all,
I'm preprocessing functional images, and after normalization to standard template with FLIRT my workmates and I are founding added correlation in the Z axis (not allowed for our study). The register has been: 1) FLIRT functional to ref:anatomical 6dof, 2) FLIRT anatomical to ref:standard 12 dof, 3) convert_xfm to concatenate the transformations leading to func.2std, and 4) FLIRT functional
to standard 12 dof with -applyxfm -init func.2std, all with trilinear interpolation).
We are guessing that maybe the added correlation in Z axis it's due to interpolation. Trying to undo that interpolation, I returned the functional image to its original resolution (after normalization, it had the resolution of the template). For that I created a template with fslcreatehd and I used FLIRT with an identity transformation, also trilinear interpolation. With this strategy there is much less added correlation in Z-axis.
Do you have any idea to further reduce the added correlation in Z-axis or avoid it during normalization? My images have an anisotropic relation of 4 and the standard template has 4.15.