[Insight-users] gradient calculation

[cagatay bilgin]

Thank you for the response Matt,

I am able to obtain better results for my
problem on synthetic data with equal spacing.

This filter has a function SetUseImageSpacing. What I am wondering
is the relationship between the spacing and the sigma value I
should be providing. The other parameters are making perfect
sense to me, as I decrease the maximum error parameter the
kernel width should going to increase.

As an example:
If for my synthetic data with equal spacing (1,1,1), I use sigma=3,
should I be using sigma=1.5 for a spacing of  (0.5,0.5,0.5) with
UseImageSpacing turned on?  It looks like the filter internally
divides the spacing with the spacing when this flag is on.
I would appreciate insights to this function.

Kind regards,
Cagatay

On Wed, Sep 28, 2011 at 11:47 AM, Matt McCormick <matt.mccormick at kitware.com
> wrote:

> Hi Cagatay,
>
> > My question:
> > Is there a filter in ITK that performs the traditional and more accurate
> > convolution ?
>
>
> http://www.itk.org/Doxygen/html/classitk_1_1DiscreteGaussianDerivativeImageFilter.html
>
>  I am doing some
> > curvature calculation in 3D and need to be as accurate as possible. Also,
> > how do I deal with
> > different z spacing using this class or other gradient filters ?
>
> This is difficult to do without resampling because the itk Image
> assumes uniform spacing.
>
> Matt
>
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