Elastix non-rigid transform displaying in the wrong area?

Support
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1

Hello Slicer team -

I have performed a rigid registration using elastix of two spine images and thought I would try doing a non-rigid registration on the same images to see if it improves my result further. I hardened the rigid registration transforms and then performed a non-rigid registration. The registration completed successfully but when I ask to see the results, the deformed grid does not overlap the registration images. The output volume, however, does appear to be deformed as I expected. So I’m beginning to suspect that the transform just isn’t displaying in the correct location? But I wanted to run it by this group and see if there’s something I’m not thinking of. Let me show you some images.

Here is the fixed image (with the non-rigid transformation grid):
image

Here is the moving image (note, it’s basically in the same location as the fixed image already because they were registered to each other previously):
image

Here is the output image from elastix (the outputVolumeNode):
image

So what I’m wondering is, why isn’t the visualization of the transform on top of the images that are transformed?

Let me know if more data would help. I can send the images, elastix parameters, elastix log files/results, etc.

2

Does the transform appear in correct location if you enable Advanced / Force grid output transform option?