[Insight-users] Silly questions about registration

[David Holmes]

I'm going over the registration framework for ITK and
running some tests so that I better understand the
model.  I have several silly questions.   

     (1)     Pulling the code from Registration1
example, I took two images that were the same, applied
translations, and ran the registration.  Here is how
it
        progressed:

        0 = 2690.87 : [2.05794, -3.43]
        1 = 3538.93 : [2.79055, -7.36234]
        2 = 3945.74 : [1.41266, -11.1175]
        3 = 4030.27 : [1.45081, -15.1173]
        4 = 4296.43 : [0.881159, -19.0766]
        5 = 4622.25 : [-1.29036, -22.4358]
        6 = 4726.89 : [-3.55759, -25.7312]
        7 = 5030.82 : [-5.44799, -29.2563]
        8 = 5368.15 : [-8.17364, -32.1839]
        9 = 5666.88 : [-10.8422, -35.1636]
        .
        .
        .

     As you can see, it looks like it is maximizing,
even though I am using the Means Squared metric.  So I
explicitly set the MaximizeOff flag-Same response. 
So,
     for kicks, I tried MaximizeOn().  Here?s what I
got:

         

        0 = 2690.87 : [-2.05794, 3.43]
        1 = 898.249 : [-4.63303, 6.49087]
        2 = 1243.98 : [-3.05864, 5.25746]
        3 = 27.0703 : [-2.62099, 3.30593]
        4 = 720.144 : [-2.93342, 4.25587]
        5 = 200.952 : [-3.01993, 5.25212]
        6 = 24.1303 : [-2.99806, 4.7526]
        7 = 22.6493 : [-2.99862, 5.0026]
        8 = 0.309667 : [-3.11456, 4.95589]

     Is something perhaps backwards there, or I am all
messed up?

         

     (2)     Using the example out of the software
guide again, this question is about what is returned. 
Generally speak, with Analyze, when we provide a
        solution to a registration, we provide the
solution that will be applied to the "moving" image to
put it into the space of the fixed image.  In my own
code using ITK, when I apply a translation of [-3,5]
to an image and then register it, the solution is
[-3,5].  If I were to apply that to the "moving"
image, the result would be a translation of [-6,10],
so at least the way that I am used to doing it, I
would have to take the negative of the solution to put
the moving into the fixed space.  I checked the
software guide and found that this is consistent with
the examples.  Once again, am I all screwed up with
this??

  Thanks for the help

   

  david

         

    

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