[Insight-users] Re: Error with Watershed Segmentation Example

[Luis Ibanez]

Hi Neha,


Thanks for posting your images and the description of your problem.

We tried passing your image as input to the Watershed example, but it
happens that your tumor58.raw image has a *constant zero value* in all
pixels.


      Please verify the source where you obtained this image.


---

Regarding the error message that you got,
it is clearly indicating that your threshold value is *too high*:

 >
 > itk::watershed::SegmentTreeGenerator::MergeSegments::
 > An unexpected and fatal error has occurred. This is probably the
 > result of overthresholding of the input image.
 >

You are setting a threshold value that is HIGHER than that water level,
this is incorrect. The threshold value should be lower than the water
level.

Please try values like


     Threshold   =  0.01
     Water level  =  0.05  to 0.2


Please read the description of this example in the
ITK Software Guide

      http://www.itk.org/ItkSoftwareGuide.pdf

Section 9.2, pdf-page 356.



Regards,


     Luis


=================

neha k wrote:

> Hello Luis,
> 
> Can I use watershed example (from ITK1.8\Examples) with Brain MRIs (Raw 
> format)?  When I try to use Watershed example on Brain MRI with tumour, 
> with following parameters range- 
> 
> Conductance Term -> 1-4, No. of Iterations - 3 - 10, Threshold (%) - 0.0 
> - 0.3, Level Of Watershed 0.01 - 0.05,
> Principle Componenet Analysys - On. I am not sure if I need to use 
> Principle Componenet Analysys.
> 
> I get following error: ------>
> 
> itk::ExceptionObject (0104F288)
> Location: "Unknown"
> File: 
> C:\ITK_1.8\InsightToolkit-1.8.0\Code\Algorithms\itkWatershedSegmentTreeGen
> erator.txx
> Line: 436
> Description: itk::ERROR: 
> itk::watershed::SegmentTreeGenerator::MergeSegments:: A
> n unexpected and fatal error has occurred. This is probably the result 
> of overth
> resholding of the input image.
> 
> Do you have any suggestions?  I have attached the image. 
> 
> Thanks.
>