Replies: 8 comments 25 replies
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Can you post the original images and the commands that you used to generate the affine transform? |
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The epi and corrected corrected_fsems images don't reside in the same physical space (specifically, they don't share the same origin) so the affine transform derived from the "corrected_fsems" pair wouldn't apply to the epi images. Try fixing this issue and see if that corrects the problem. |
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No, the origin in either image isn't changed. The calculated initial transform simply matches the fixed and moving image origins.
See further discussion here.
https://itk.org/Doxygen/html/classitk_1_1AffineTransform.html |
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Again, you'd have to post the commands and images for us. |
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Please include a script file that I can use to simply run from the command line. |
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I didn't have any issues running the command. Make sure your ANTs is up-to-date with the repository.
|
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For this specific imaging pair, you will probably need to have both brains extracted. |
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yes.
You shouldn't. It's not a usable feature at this point in time. |
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Hi,
I try to apply the affine transformation file and the deformation field estimated from two high-resolution 3D T2-weighted images (matrix size = 256x128x16, FOV=24mmx12mmx8mm) to low-resolution functional images (matrix size = 96x48x16, FOV=24mmx12mmx8mm) by using
antsApplyTransforms -d 3 -e 3 --interpolation BSpline[5] -t run0_1Warp.nii.gz -t run0_0GenericAffine.mat -i epi.nii, -r epi.nii, -o epi_warped.nii
However, the warped epi images don't match the images that I want to register to. I thought it was the image origin mismatch causing the failure of the registration, i.e. the image origin of the fixed images used to estimate the transformation files is not the same as that for the epi images (I assume the default of origin when using "antsApplyTransforms" is the geometric center of the image). Then I tried to change
--initial-fixed-transform [fixedImg, movingImg, 1]
to--initial-fixed-transform [fixedImg, movingImg, 0]
to use the geometric center of the images. The result is incorrect, either.Then I tried to register one epi image to the other directly and got the run1_0GenericAffine.mat. I compared it to run0_0GenericAffine.mat. Initially, I thought the parameter AffineTransform_double_3_3 in both files should be close because the T2w images and epi images have the same FOV and image center, i.e. they are registered already except epi images bear more distortion. Surprisingly, the two _oGenericAffine.mat files are quite different, especially for the last three numbers (which according to the manual, are the translation parameters). Here are the results:
I'm quite confused about the results. Could any experts explain to me why I got such results and also enlighten me how to apply transformation files estimated from high-resolution images to the corresponding low-resolution images?
Thanks
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