How to constrain an affine transform? #875
Replies: 3 comments
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Hi @raacampbell, what I would try is to set the
I would try a "dry-run" with maximum iterations =1 and (AutomaticScalesEstimation "true"), then I would copy the That is just an idea though. Maybe somebody else has a better one or has tried it before. |
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I tried scales and it seemed to make no difference but I might have done it wrong. What did help, however, was translation only reg (not affine). I still need to set to 0 one of the parameters but overall the reg works better even without that. |
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I created a notebook example on how to use scales for that purpose (https://github.com/InsightSoftwareConsortium/ITKElastix/blob/main/examples/ITK_Example21_ConstrainedRegistration.ipynb). @raacampbell, could you take a look? |
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I am registering two 3D images. Due to the way the images are generated I know only certain transformations are physically possible. e.g. I can have translation in Y and Z but not X. Differences in scale and rotation between my images are not possible.
My results are not as good as expected and the main thing going wrong at the moment is that Elastix is calculating a non-zero X translation. I verified this by manually setting this parameter to zero and re-transforming the image with
transformix
.Is there any way I can constrain my registration? Presumably I will get a better result this way compared to setting parameters to zero post hoc.
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