Image registration nrrd files appear to be scaled differently despite adjusting scaling

elrond11
Wed, 22 Mar 2023 01:35:34 +0000
Support

I have been using 3D Slicer for rigid registration of two nrrd volumes. The first is an STL file that I have rasterized into an nrrd file within Slicer, this is the fixed image. The second nrrd file, moving image, has been resampled to match the fixed image file in Python. When I open the two files, the fixed image has image spacing units already encoded in Slicer. The moving image has the default of 1 which I set to match the spacing units of the fixed image. This has generally been fine for my registration workflow but for some files I have noticed the fixed image seems to still have features larger then the moving image even after adjusting the image spacing. Is there a way to fix this automatically in Slicer or Python?

Example included below. The overlay is the fixed image which seems to have image features much larger then what’s in the moving image.

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