Remove atifacts background after registration

After rigid registration using Elastix, I got CT data with artifacts at background

is there any way to remove background remaining only head volume?

If you selected an output transform node, then instead of using the output volume, apply the transform on the moving volume.

Thank you for the reply!

It removes the background, but the demension and spacing do not fit with MR data.
What should be done after applying the transform node?

You probably didn’t actually apply the transform on the moving volume.

It can be done from the Data module (right-click the transform column ans select the transform) or the Transforms module (select transform, and move the volume under it)