[Insight-users] Scalar Speed Image in Level Set Approaches

[droettger at uni-koblenz.de]

Hey,

thanks so far. Did you read my question in terms of the advection term.
I posted it earlier.
I have still problems with the advection field.
Here is what I wrote:

Hey Luca,

thaks for your help so far. I see how the different terms work.
I've tried th SetAdvectionImage method, but I didn't succeed.

Here are parts out of my code:

typedef itk::CovariantVector< double, 3 >  GradientPixelType;
typedef itk::Image< GradientPixelType, 3> GradientImageType;

typedef itk::GradientVectorFlowImageFilter<GradientImageType,
	GradientImageType> GVFFilterType;

GradientImageType::Pointer m_GVFField;

m_GVFField = gradientVectorFlow->GetOutput();

geodesicActiveContour->SetAdvectionImage(m_GVFField);

This is what you meant, right?

Regards,
Diana

>
>
> Hi Diana,
>
> You have (at least) two options:
>
> 1) Use the Advection field term in the Geodesic Active Contours.
>     Normally, the vector field that represents the advection term
>     will help to push back the level set when it goes too far from
>     the border (... as long as there is actually a border there...)
>
> 2) You can have negative speed terms, but that may require that you
>     retouch (e.g. derive and overload some methods) from the level set
>     function.
>
>     You may want to look at how this is done in the
>     ThresholdSegmentationLevelSetFunction
>
>
>   Please let us know if you have further questions,
>
>
>       Thanks
>
>
>          Luis
>
>
> --------------------------------
> droettger at uni-koblenz.de wrote:
>> Hey,
>>
>> I'm testing ITK level set approaches in my segmentation framework and
>> want
>> the front to shrink, when it crosses over boundaries.
>> Is it possible to manipulate the scalar speed image to be negative in
>> some
>> cases, for example at some specific intensity values, on my own and pass
>> positive as well as negative values in the speed image to the level set
>> algorithm?
>>
>> Is it possible in all level set methods, for example
>> ShapeDetectionLevelSetImageFilter or
>> GeodesicActiveContourLevelSetImageFilter?
>>
>> Thanks!
>> Best regards,
>> Diana
>>
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>