Edit Deformations

Add a deformation field to an image or edit/remove an existing one.

Input

This algorithm requires an image, volume or set containing any combination thereof. The input may not already have an attached deformation.

Output

Changes the deformation field attachment of the input image. No images will be added to the data model.

Description

The algorithm allows to add, remove and edit the deformation field of an image. A deformation can be used to transform the world position of pixels so that they are no longer arranged in a rectilinear grid. Attention: Deformation fields are only considered by algorithms that support the deformation attachment of images.

Select a deformation model and click the [Add] button to add a new deformation to the image. The Edit Deformations controller supports the following deformation models:

  • Free-Form Deformation: Defines the deformation based on a fixed rectilinear grid of control points. You can specify the size, location and resolution of that grid. The local deformation for each pixel is given by bilinear/trilinear interpolation of the surrounding control points.
  • Thin-Plate Splines: Defines the deformation based on Thin Plate splines. You can define control points at arbitrary locations. The local deformation for each pixel is given by Thin Plate Spline interpolation of the surrounding control points based on the Regularizer weight parameter.
  • Dense Deformation Field: Defines the deformation based on a dense deformation field provided by a three-channel source image. Each pixel of the source image describes the local deformation at the corresponding location of the input image.

You can interactively define the deformation field parameters (i.e. the control points) in the views showing the input image.

To remove the deformation again, click on the [Remove] button. Note that this will delete the deformation for good and this cannot be undone!

If you want to save the deformation or compare different deformations, open the ‘Stored Deformations’ sections. In here you can save, delete and restore deformations with the three buttons on the right. Be aware that Dense Deformations can get fairly large and may consume a lot of memory. Closing the ‘Edit Deformations’ algorithm will clear the ‘Stored Deformations’, i.e. they won’t be available when opening the algorithm again.

Sometimes it might be necessary to apply a single deformation onto several images. For example you might have T1 and T2 MRI that you want to register to an ultrasound. The two MRI images are already perfectly aligned but need to be deformed to match the ultrasound. In this case it makes sense to first add a deformation to the T1, then open the ‘Edit Deformations’ algorithm on the T2, click on the [Link] button and select the T1 image from the list. The deformations of the two images are now ‘linked’, i.e. changing one simultaneously changes the other one as well.

See also