[ITK-users] Inverse of Versor Rigid Transform and RIRE
Gabriel A. Giménez
gabrielgimenez85 at gmail.com
Thu Apr 9 21:17:21 EDT 2015
Hi Matt!
If you are working with a current version of ITK, when you get the
> inverse transform, it should transfer the Center for you. The Center
> point locations are the FixedParameters for the parent class,
> MatrixOffsetTransformBase. The relationship with parent classes can be
> found by examining the Doxygen page for the class [1].
I took a few days to read the RIRE documentation and I came to the
conclusion that the direction of registration is not really
relevant...taking up CT as the fexed image and MR as the moving image can
be used the transformation that provides ITK...without having to calculate
the inverse.
Do you get the same result by applying the TransformPoint() method of
> the inverse transform? This is the API call that should be applied to
> transform a point.
Yes Matt, I get the same results using the API.
But...I made some changes in my optimizers and I got very good results,
like this ( with RegularStepGradientDescentOptimizerv4 and
MattesMutualInformationImageToImageMetricv4):
iterations = 200
Metric value = -0.709388
versor X = 0.0155583
versor Y = 0.00642035
versor Z = -0.0487144
Translation X = 7.82977
Translation Y = -60.1034
Translation Z = -23.6258
+-----------------------------------------------------------------------------------------------+
| X GT| Y GT| Z GT| X R|
Y R| Z R|
-----------------------------------------------------------------------------------------------+
| -7.573100| -41.253400| -27.309300| -7.661395|
-40.915138| -26.044441|
| 324.872200| -72.815900| -32.906300| 324.712907|
-73.345104| -30.833635|
| 24.160700| 291.039300| -16.272700| 24.902019|
291.325008| -15.874605|
| 356.606000| 259.476800| -21.869700| 357.276322|
258.895042| -20.663798|
| -6.055400| -45.115700| 84.613700| -6.394922|
-44.465633| 85.892103|
| 326.389900| -76.678200| 79.016800| 325.979381|
-76.895599| 81.102910|
| 25.678400| 287.176900| 95.650300| 26.168493|
287.774513| 96.061940|
| 358.123700| 255.614500| 90.053400| 358.542796|
255.344547| 91.272747|
+-----------------------------------------------------------------------------------------------+
[X, Y, Z]GT are the "ground truth" values and [X, Y, Z]R are my results
Now, something I find strange is that when increasing the number of
iterations...metric value limprovement is too little but the result is
little worse..., example:
Iterations = 334
Metric value = -0.710918
versor X = 0.0216566
versor Y = 0.00700629
versor Z = -0.0508766
Translation X = 7.80722
Translation Y = -60.5124
Translation Z = -24.1047
+-----------------------------------------------------------------------------------------------+
| X GT| Y GT| Z GT| X R|
Y R| Z R|
+-----------------------------------------------------------------------------------------------+
| -7.573100| -41.253400| -27.309300| -8.342271|
-39.764911| -28.121895|
| 324.872200| -72.815900| -32.906300| 323.882938|
-73.594962| -33.530625|
| 24.160700| 291.039300| -16.272700| 25.690487|
292.179801| -13.916412|
| 356.606000| 259.476800| -21.869700| 357.915696|
258.349750| -19.325143|
| -6.055400| -45.115700| 84.613700| -7.022108|
-44.688304| 83.762051|
| 326.389900| -76.678200| 79.016800| 325.203101|
-78.518355| 78.353321|
| 25.678400| 287.176900| 95.650300| 27.010650|
287.256408| 97.967534|
| 358.123700| 255.614500| 90.053400| 359.235859|
253.426357| 92.558803|
+-----------------------------------------------------------------------------------------------+
This pattern is repeated with other optimizers ( like OnePlusOne and a GA
approach that I am implementing ), that you think about it?
Other questions Matt...:
How works the multithreaded in metrics ? is customizable? improve
performance? specifically in the case of Mattes Mutual Information...
I tried using the helper CenteredVersorTransformInitializer... but the
transformation that generates makes, incredibly and also very strange,the
optimizers does not advance...using CenteredTransformInitializer this does
not happen...
Really Thanks in advance Matt!
Regards,
2015-04-07 15:03 GMT-04:00 Matt McCormick <matt.mccormick at kitware.com>:
> Hi Gabriel!
>
> > I am use RIRE project, specifically CT (movig) and MR_PD (fixed) images.
> > Basically, I hava a set of point (in millimeters) of the CT image to
> which
> > apply the trasform result of the registration and updaload this results
> in
> > the web for the evaluation. Example of set of points and his "ground
> truth"
> > :
> >
> > Point x y z new_x new_y new_z
> >
> > 1 0.0000 0.0000 0.0000 -7.5731 -41.2534 -27.3093
> > 2 333.9870 0.0000 0.0000 324.8722 -72.8159 -32.9063
> > 3 0.0000 333.9870 0.0000 24.1607 291.0393 -16.2727
> > 4 333.9870 333.9870 0.0000 356.6060 259.4768 -21.8697
> > 5 0.0000 0.0000 112.0000 -6.0554 -45.1157 84.6137
> > 6 333.9870 0.0000 112.0000 326.3899 -76.6782 79.0168
> > 7 0.0000 333.9870 112.0000 25.6784 287.1769 95.6503
> > 8 333.9870 333.9870 112.0000 358.1237 255.6145 90.0534
>
> Trying to reproduce previous results is a good path forward.
>
> > So, the first I need is the transformation to apply, for that I do the
> > following :
> >
> > //get the inverse transform
> > TransformType::Pointer inverseTransform = TransformType::New();
> > inverseTransform->SetCenter( finalTransform->GetCenter() );
> > bool response = finalTransform->GetInverse(inverseTransform);
> >
> >
> > It makes sense to use the same center in the inverse transform?. A
> > "quaternion" define an "axis" (right part) of rotation and an angle to
> use
> > for rotate the image about this axis...why use a center of rotation...?
>
> If you are working with a current version of ITK, when you get the
> inverse transform, it should transfer the Center for you. The Center
> point locations are the FixedParameters for the parent class,
> MatrixOffsetTransformBase. The relationship with parent classes can be
> found by examining the Doxygen page for the class [1].
>
>
> > Second, apply this transform...as follows:
> >
> > NewPoint = RotationMatrix * OriginalPoint + Offset
> >
> > The rotation matrix and the offset are obtained from the inverse
> transforme
> > objetc. Found something wrong? something that is not taking into account
> ?
> > The results do not appear to be correct...the calculated error is too big
> > and does not correspond with the visual result.
>
> Do you get the same result by applying the TransformPoint() method of
> the inverse transform? This is the API call that should be applied to
> transform a point.
>
> Thanks,
> Matt
>
>
> [1]
> http://www.itk.org/Doxygen/html/classitk_1_1VersorRigid3DTransform.html
>
--
*Gabriel Alberto Giménez.*
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