Issue with NIfTI spatial transforms
Opened this issue · 1 comments
neurolabusc commented
dcm2niix issue 718 appears to suggest that the itksnap tools have issues with NIfTI spatial transforms.
To replicate a minimal example, you consider the NIfTI image ax_asc_35sl_6.nii which appears correctly in FSLeyes, MRIcroGL and itksnap. The header specifies a LAS orientation:
fslhd ax_asc_35sl_6.nii
...
sto_xyz:1 -3.250000 0.000000 -0.000000 104.000000
sto_xyz:2 0.000000 3.230991 -0.388798 -58.684311
sto_xyz:3 0.000000 0.350998 3.578943 -84.798035
sto_xyz:4 0.000000 0.000000 0.000000 1.000000
sform_xorient Right-to-Left
sform_yorient Posterior-to-Anterior
sform_zorient Inferior-to-Superior
However, operations with c3d creates a NIfTI header that suggests an LPS image, and the resulting image appears flipped in the Anterior-Posterior (row) direction in FSLeyes, MRIcroGL and itksnap:
c3d ax_asc_35sl_6.nii -mean -o mean.nii
...
sto_xyz:1 -3.250000 0.000000 0.000000 104.000000
sto_xyz:2 0.000000 -3.250000 0.000000 -58.684311
sto_xyz:3 0.000000 0.000000 3.600000 -84.798035
sto_xyz:4 0.000000 0.000000 0.000000 1.000000
sform_xorient Right-to-Left
sform_yorient Anterior-to-Posterior
sform_zorient Inferior-to-Superior
I am not sure how to determine the c3d version, but I installed it today from c3d-nightly-MacOS-arm64.dmg.
pyushkevich commented
Hi Chris,
This is an interesting error. It has to do with the image being a 4D image.
If you run c4d on the image, the orientation is correct.
c4d ax_asc_35sl_6.nii -mean -o mean.nii
But if you run c3d, then it does output a 3D image with the reversed
orientation. This seems to be related to how an ITK ImageFileReader
templated for 3d images reads the NIFTI header.
A solution may be to add a warning to c3d when it is asked to read a 4D
(3d+time) image?
Paul
…On Sat, Sep 9, 2023 at 10:35 AM Chris Rorden ***@***.***> wrote:
dcm2niix issue 718 <rordenlab/dcm2niix#718>
appears to suggest that the itksnap tools have issues with NIfTI spatial
transforms.
To replicate a minimal example, you consider the NIfTI image
ax_asc_35sl_6.nii
<https://github.com/neurolabusc/dcm_qa/blob/master/Ref/ax_asc_35sl_6.nii>
which appears correctly in FSLeyes, MRIcroGL and itksnap. The header
specifies a LAS orientation:
fslhd ax_asc_35sl_6.nii
...
sto_xyz:1 -3.250000 0.000000 -0.000000 104.000000
sto_xyz:2 0.000000 3.230991 -0.388798 -58.684311
sto_xyz:3 0.000000 0.350998 3.578943 -84.798035
sto_xyz:4 0.000000 0.000000 0.000000 1.000000
sform_xorient Right-to-Left
sform_yorient Posterior-to-Anterior
sform_zorient Inferior-to-Superior
However, operations with c3d creates a NIfTI header that suggests an LPS
image, and the resulting image appears flipped in the Anterior-Posterior
(row) direction in FSLeyes, MRIcroGL and itksnap:
c3d ax_asc_35sl_6.nii -mean -o mean.nii
...
sto_xyz:1 -3.250000 0.000000 0.000000 104.000000
sto_xyz:2 0.000000 -3.250000 0.000000 -58.684311
sto_xyz:3 0.000000 0.000000 3.600000 -84.798035
sto_xyz:4 0.000000 0.000000 0.000000 1.000000
sform_xorient Right-to-Left
sform_yorient Anterior-to-Posterior
sform_zorient Inferior-to-Superior
I am not sure how to determine the c3d version, but I installed it today
from c3d-nightly-MacOS-arm64.dmg
<https://sourceforge.net/p/c3d/git/ci/master/tree/doc/c3d.md>.
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