[ITK-users] How to get inverse diffeomorphic demons deformation field transform?

[Mathew Guilfoyle]

I am using (Simple)ITK DiffeomorphicDemonsRegistrationFilter() to perform deformable registration of two 3D images.  This works fine.  Output from the filter is 'outImage' vector image which I then convert to a transform using 

dfTransform = DisplacementFieldTransform(outImage).  

I can then resample my moving image using this transform and all looks as expected.

My reading/understanding of diffeomorphic algorithms is that there should be an exact and readily computable inverse transform?  I need this as I want to inverse warp a template segmentation performed on my reference image into the original space of my moving image.  How do I obtain the inverse DisplacementFieldTransform or the inverse vector image?

I have tried the InvertDisplacementField filter but the output of this does not appear to correctly invert my warped image back to the original so I do not think this filter generates is a n accurate inverse, at least using default settings.

Any ideas of if/how I can get an exact inverse of a deformable transform?

Thanks