[Insight-users] Re: Anisotropic diffusion filter class (rashed karim)

[johnjtchen at aol.co.uk]

Hi Rashed,

I use GradientAnisotropicDiffusionImageFilter quite intensively in my application as the preprocessing step for segmentation. I think the parameters depends on what post steps you are going to do. So the best way probably to get the best parameter combinations is to try it yourself.? Usually I can get pretty good results from the default parameter settings in T1 image, and slightly tweaking iterations and conductance rate on FLAIR modality due to partial volume effect. Tuning iterations will make image more blured and conductance rate constrains the fuzziness of edges. As for timestep I left it remains default ? m_TimeStep = 0.5 / vcl_pow(2.0, static_cast<double>(ImageDimension));. Following are the comments copy and paste from sourcecode:

?*? \par Parameters
?*? Set/GetNumberOfIterations specifies the number of iterations (time-step updates)
?*? that the solver will perform to produce a solution image.? The appropriate
?*? number of iterations is dependent on the application and the image being
?*? processed.? As a general rule, the more iterations performed, the more
?*? diffused the image will become.
?*
?*? \par
?*? Set/GetTimeStep sets the time step to be used for each iteration (update).
?*? This parameter is described in detail in itkAnisotropicDiffusionFunction.
?*? The time step is constrained at run-time to keep the solution stable.? In
?*? general, the time step should be at or below 1/2^N, where N is the
?*? dimensionality of the image.
?*
?*? \par
?*? Set/GetConductanceParameter set a common parameter used by subclasses of
?*? itkAnisotropicDiffusionFunction.?? See itkAnisotropicDiffusionFunction for
?*? detailed information.


HTH
john


Hi everyone,

I am trying to use the tkGradientAnisotropicDiffusionImageFilter class.  I
cannot figure out what values to use for its parameters. What numbers
typically are used for number of iterations, conductance and time step?

Thanks,
Rashed karim.

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