[Insight-users] mapping points from moving image to fixed image

[Luis Ibanez]

Hi John,

1) The Deformation Field resulting from a Deformable Registration
     process in ITK, contains the vectors that point from the physical
     coordinates of a point in the Fixed image reference system to
     its corresponding point in the Moving image reference system.

2)  You could combine that deformation field with the WarpImageFilter
     in order to map intensities from the Moving image reference system
     into the Fixed Image reference system. That is: to resample the
     Moving image into the image grid of the Fixed image.

3)  If you want to map points (not pixel values) from the Moving image
     to the Fixed image, then you need to invert the deformation field.
     Simply negating (multiplying by -1 ) the initial deformation field
     will NOT do the trick.

4)  You may want to look at the following two options for inverting
     deformation fields:

4.1)  Insight/Code/BasicFilters/itkInverseDeformationFieldImageFilter.h

4.2)  Insight/Code/BasicFilters/itkIterativeInverseDeformationFieldImageFilter.h

     The first method uses a KernelTransform ( such as ThinPlateSplines)
      as an intermediate helper for computing the inverse field.

      The second method computes the inverse field iterative based
      on   F * R = I  (forward field composed with Reverse field should
      be equal to the Identity), by redistributing the residual errors of
      Error = F * R - I


5) An alternative option can be found in

     InsightApplications/InverseConsistentLandmarkRegistration

     Based on the paper:

Consistent Landmark and Intensity-Based Image Registration
by H. J. Johnson* and G. E. Christensen
IEEE TRANSACTIONS ON MEDICAL IMAGING, VOL. 21, NO. 5, MAY 2002



Please give it a try and let us know if you find
any problems.



     Thanks


          Luis


--------------------------------------------------------
On Sat, Oct 10, 2009 at 4:12 AM, John Drozd <john.drozd at gmail.com> wrote:
> Hello,
>
> I used deformable registration using DeformableRegistration8.cxx to register
> one brain subject from one person with another brain subject from another
> person.  I now have a deformation field file that was outputted from
> deformableregistration8.cxx.  I was reading on the internet the following
> link http://www.itk.org/pipermail/insight-users/2009-April/030004.html that
> describes how to map points from the fixed image to the moving image using a
> deformation field.  If i want to map points from the moving image to the
> fixed image, can I use the same procedure but take the negative of the
> deformation field, and if so how can i negate the deformation field and use
> it with ResampleImagefilter? My logic is that when you take the negative of
> a vector, this reverses its direction.
>
> Thank you,
>
> john
>
>
>
>
> --
> John Drozd
> Postdoctoral Fellow
> Imaging Research Laboratories
> Robarts Research Institute
> Room 1256
> 100 Perth Drive
> London, Ontario, Canada
> N6A 5K8
> (519) 661-2111 ext. 25306
>