# How to handle images defined in left-handed coordinate system

**URL:** https://discourse.slicer.org/t/how-to-handle-images-defined-in-left-handed-coordinate-system/4133
**Category:** Development
**Created:** [September 17, 2018, 9:10pm UTC](https://discourse.slicer.org/t/how-to-handle-images-defined-in-left-handed-coordinate-system/4133 "2018-09-17T21:10:04Z")
**Posts on this page:** 1
**Showing post:** 2

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### Author: ![lassoan](https://sea2.discourse-cdn.com/flex002/user_avatar/discourse.slicer.org/lassoan/32/13_2.png) [@lassoan](https://discourse.slicer.org/u/lassoan)
#### Post date: [September 17, 2018, 9:26pm UTC](https://discourse.slicer.org/t/how-to-handle-images-defined-in-left-handed-coordinate-system/4133/2 "2018-09-17T21:26:10Z")

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> [@How to convert to .stl from .nii](https://discourse.slicer.org/t/how-to-convert-to-stl-from-nii/4088/4):
>
> voxel-to-physical coordinate system that describes acquisition geometry can be left handed

From [this specification](https://nifti.nimh.nih.gov/nifti-1/documentation/nifti1fields/nifti1fields_pages/qsform.html) it seems that left-handed is not permitted in nifti (search for left-handed on the page and see also axes specification a few paragraphs above).

> [@How to convert to .stl from .nii](https://discourse.slicer.org/t/how-to-convert-to-stl-from-nii/4088/4):
>
> ITK readers re-arrange the data to enforce right-handedness

Is this something that has been added recently? What direction matrix do you see in Volumes module when you load the above-referenced volume into Slicer?

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