# Clarification on HCP MNI nonlinear warps and tcktransform (incorrect scaling on single axis?)

**URL:** <https://community.mrtrix.org/t/clarification-on-hcp-mni-nonlinear-warps-and-tcktransform-incorrect-scaling-on-single-axis/2857>\
**Category:** Uncategorized\
**Created:** [September 27, 2019, 3:54am UTC](https://community.mrtrix.org/t/clarification-on-hcp-mni-nonlinear-warps-and-tcktransform-incorrect-scaling-on-single-axis/2857 "2019-09-27T03:54:45Z")\
**Posts on this page:** 1\
**Showing post:** 5

<div class="post-metadata">

**Author:** ![kjamison](https://community.mrtrix.org/letter_avatar_proxy/v4/letter/k/848f3c/32.png) [@kjamison](https://community.mrtrix.org/u/kjamison)\
**Post date:** [December 9, 2019, 3:49pm UTC](https://community.mrtrix.org/t/clarification-on-hcp-mni-nonlinear-warps-and-tcktransform-incorrect-scaling-on-single-axis/2857/5 "2019-12-09T15:49:45Z")

</div>

OK it’s been a while but I’m looking into this issue again. I think I resolved the problem but wanted to update this post in case somebody else encounters the same thing. It’s a little confusing why this is the specific symptom, but if you swap the x-axis of the transform before applying, the x-axis shrinking no longer occurs:

```auto
mrconvert standard2acpc_dc.nii.gz tmp-[].nii -force
mv tmp-0.nii x.nii
mrcalc x.nii -neg tmp-0.nii -force
warpconvert tmp-[].nii displacement2deformation mni2acpc_mrtrix.nii.gz -force
rm x.nii tmp-?.nii

tcktransform mytracks.tck mni2acpc_mrtrix.nii.gz mytracks_mni.tck -force

```

---

_[View the full topic](https://community.mrtrix.org/t/clarification-on-hcp-mni-nonlinear-warps-and-tcktransform-incorrect-scaling-on-single-axis/2857)._