[Insight-users] ImageRegistration example from the ItkSoftwareGuide?

[Luis Ibanez]

Hi Motes,


Despite the apparent contradiction,
these two statements are saying the same thing.


This is explained in more detail in

    Section 8.3.1.
    "Direction of the Transform Mapping"
    in pdf-page 359.


Let me summarize it as:


    A) The Transform resulting from the registration
       process is such that it maps points from the
       coordinate system of the Fixed Image into points
       in the coordinate system of the Moving Image,

    B) When you connect the transform from (A) into
       the ResampleImageFilter, and
       use the Moving image as input, and
       use the Fixed Image grid parameters
       (origin, spacing, orientation, number of pixels)

        then you can map the intensity values of the
        Moving image into a grid that is collocated
        with the coordinate system of the Fixed image.



The apparent confusion arise from the fact that in order
to bring the *intensities* of the moving image into alignment
with the fixed image, you have to first map the *coordinates*
from the Fixed image pixels to the coordinate system of the
moving image.


If you think in terms of Resampling, things become a lot
more clear.


Studying Figure 8.7 in pdf-page 358 should also help
to explain how the Transform is directed in ITK.


Please read section 8.1.1. and let us know if you still
have any questions.


      Thanks


        Luis



-------------------
motes motes wrote:
> On page 315 in the ItkSoftwareGuide Image registration is defined as:
> 
> "Registration is treated as an optimization problem with the goal of 
> finding the spatial mapping that will bring the [moving image] into 
> alignment with [the fixed image]."
> 
> But on page 317 when describing the implementation it says:
> 
> "The transform that will map the [fixed image] space into the [moving 
> image] space is defined below."
> 
> Is this not opposite to what is said on page 315? I assume it does not 
> matter as long as the two images are aligned but would like to know if I 
> have missed something.
> 
> 
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