[Insight-users] A Few Questions and Problems

[Amitesh Agarwal]

Hello,

I have been using ITK for last few months and hence come across a few
problems. I would really appreciate any help at all in this matter. At
present I am working on Image extraction from a grayscale 3D image in
.vtk file format.

1) Gradient Anisotropic Diffusion Image Filter
         I had initially used suggested values, as given in ITK 1.4
Software Guide (6.5), for number of iterations, timestep and
conductance parameter. However at runtime the filter gave a warning
that the timestep (0.125) chosen for this 3D image is unstable one and
the minimum stable timestep is (0.0625). I accordingly did the same. 
It is my understanding that the filter has come from the solution of
heat diffusion equation and timestep delta t in the CFL condition
determines stability or unstability of a particular implementation of
a computational scheme. My question is that In that situation How can
I find a stable timestep for a particular image for Image processing
purpose?

2) Sigmoid Image Filter

Is there any method by which I can find the optimum value alpha and
beta for a 3D image so that I can obtain best result. Will that be
possible in ITK? Is there any similar implementation anywhere in the
form of piece/chunk of code?

3) Removal of Cryogenic Gel

At present I am stuck in the problem of removal of Cryogenic gel from
the dataset. I am not sure how it can be done in ITK but to me it
seems that the best possible way it could be done would be using flood
fill with zero intensity pixels in the gel area with a single seed
point (if it could somehow be done in ITK!!). Some details about
removing the cryo gel has been mentioned In the ITK book (About the
cover Page) but it is not very clear to me. Can anybody help me with
that?

4) Opening and closing operation in a binary image

I just wanted to know if there is any filter present in ITK for
performing opening and closing operation in a given Binary Image. It
is my understanding that BinaryErode and BinaryDilate do similar
operation in effect but not exactly the same.

Regards

Amitesh