[Insight-users] Spacing and itk::RecursiveGaussianImageFilter

[Bc. Michal Srna]

Hello,
I would like to ask you, if itk::RecursiveGaussianImageFilter takes account
in a spacing of image?

For example, if I creatre filterX, filterY and filterZ via
itk::RecursiveGaussianImageFilter and have spacingX, spacingY and spacingZ,
does itk::RecursiveGaussianImageFilter recalculates the sigma parameter in
dependence of spacing, which differs in direction X,Y,Z?

Here is the example: I have sigma=3 and set it via:

filterX->SetSigma(sigma);
filterY->SetSigma(sigma);
filterZ->SetSigma(sigma);

does it mean, that in all directions is convolution kernel of the same size?
Or does it recalculates sigma in dependece of spacingX,spacingY,spacingZ?

Why am I askig this? I need, thati if spacingZ is for example 3 times
greater then spacingX, I think, that sigma should differ too in direction Z.


I figured out this recalculation of sigma in dependece of spacing:

filterX->SetSigma(sigma);
filterY->SetSigma( (spacingY/spacingX) * sigma);
filterZ->SetSigma( (spacingZ/spacingX) * sigma);

By this recalculation, convolution kernel should cover always the same area
of pixels not depending on the spacing between pixels, is it right?



-- 
S pozdravem Bc. Michal Srna

Fotografické portfolio:
http://michalsrna.cz
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