[Elastix] Question regarding Transform Parameter file

Tom Knoop t.h.knoop at student.utwente.nl
Mon May 19 22:27:57 CEST 2014


Hi Lisa,

I might be mistaken, since my experience with elastix somewhat limited.
However, I think the information you are looking for is in the manual.
According to paragraph 2.6, the translation transform is defined as:
Tmu(x)=x+t
in this case the parameter vector mu=t (for exact formatting, see formula
2,11).

That would mean that the TransformParameters are the offsets x and y
necessary to map your fixed image to the moving image.  Since you're doing
only a translation, I think calculating the maximum shift for an image set
could be done by aggregating the transform parameters for all your images,
and look for the image with highest values. For the exact meaning and
perhaps clearer explanation, the start of paragraph 2.6 is quite
informative.

Good luck!

Best,

Tom


On Mon, May 19, 2014 at 10:00 PM, Lisa Richards <lisa.richards at utexas.edu>wrote:

> Hi all,
> I have used elastix to perform a Translation transform on a set of images,
> producing a set of Transform files in the process.  I need to calculate the
> maximum shift that occurs in the image set.  I am wondering if I can use
> the TransformParameters output in the parameter file to do this.  For one
> sample file, the Transform Parameter file is listed below.  What can I
> infer from this file?  I don’t know what the two numbers outputted as the
> TransformParameters represent and could not find definitions in the
> documentation.
> Thank you for your assistance,
> Lisa Richards
>
>>
> (Transform "TranslationTransform")
> (NumberOfParameters 2)
> *(TransformParameters -0.129060 0.143669)*
> (InitialTransformParametersFileName "NoInitialTransform")
> (HowToCombineTransforms "Compose")
>
> // Image specific
> (FixedImageDimension 2)
> (MovingImageDimension 2)
> (FixedInternalImagePixelType "float")
> (MovingInternalImagePixelType "float")
> (Size 477 642)
> (Index 0 0)
> *(Spacing 0.3527777778 0.3527777778 <3527777778>)*
> (Origin 0.0000000000 0.0000000000)
> (Direction 1.0000000000 0.0000000000 0.0000000000 1.0000000000)
> (UseDirectionCosines "true")
>
> // ResampleInterpolator specific
> (ResampleInterpolator "FinalBSplineInterpolator")
> (FinalBSplineInterpolationOrder 3)
>
> // Resampler specific
> (Resampler "DefaultResampler")
> (DefaultPixelValue 0.000000)
> (ResultImageFormat "tif")
> (ResultImagePixelType "unsigned short")
> (CompressResultImage "false")
>
>
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