[Insight-users] Fast Marching Filter produces blank output

[Charlotte Curtis]

Hi Dan, thanks for your reply,

I am confused. Are you using ITK directly, ITK filters through
> MeVisLab, or are you simply using MeVisLab to look at the result? If
> ITK directly, can you post your code?
>

I'm using ITK filters through MeVisLab, it comes with nearly all of them
implemented as modules.

The stopping value should be greater than 0.0. It is a mechanism to
> stop the algorithm before all the pixels in the image have been
> processed. If you do not set this parameter a large value is used by
> default (which typically results in the whole image being processed).
>


It was my understanding that the stopping value should be somewhere around
the values of the voxels at the edge of the region, which for me is
somewhere between 200 and 1000 HU.  I've tried using very large numbers, but
I still get nothing output.

The NormalizationFactor parameter is used to support integer speed
> functions -- the integer speed function is divided by this value to
> convert each pixel to a real. If using a real speed function, you do
> not need to set this parameter (it defaults to 1.0). It sounds like
> you are computing a real speed function, in which case it should be in
> the range [0.0,1.0] (0.0 in areas you want to the front to move
> slowly, 1.0 in areas you want the front to move quickly).
>
> SpeedConstant is used if you do not provided a speed function. The
> parameter basically allows you to compute a Euclidean distance map
> from the initial front.
>

That was basically what I thought, so I initially had values of 1 for
normalization and 0 for speed constant.  However, when I didn't get any
results, I thought I might try other values.

Can you post your input image and speed image to a web server
> somewhere? They would be very helpful trying to diagnose the problem.
>

I posted a screenshot from the program showing (left to right): the input
image, the FastMarching dialogue box, and the speed image.  It can be found
at http://www.uoguelph.ca/~curtisc/MeVisScreenshot.png<http://www.uoguelph.ca/%7Ecurtisc/MeVisScreenshot.png>
.

Thanks again,

Charlotte
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