[Insight-users] Fast Marching for arbitrary interfaces

[Luca Antiga]

Hi Armadeep,
  you should be able to initialize your front with  
FastMarchingImageFilter with different time-crossing values for every  
trial point (i.e. the initial front doesn't have to binary). In your  
case, you may want to set the value of each trial point to the value  
of the level set at that point.
When you fill your list of trial points, you have to fill out a list  
of "nodes": just call node.SetValue(someValue) in addition to  
node.SetIndex(someIndex) to set the initial time-crossing value at  
that index.
FastMarchingExtensionImageFilter does more, in that it also extends  
auxiliary variables in addition to the "time-crossing map".
I hope this helps

Luca


On May 25, 2009, at 12:10 PM, Amardeep Singh wrote:

> Dear Luis
>
> Thank you very much for your answer!
> I have also thought about using the  
> ShapeDetectionLevelSetImageFilter. But in my application, I'm  
> afraid, I am
> interested in the time-crossing map, initialized from an arbitrary  
> front. I need to
> use level-sets with an exact narrow-band (for post-processing). So,  
> the chamfer distance function which
> is currently used is not exact enough in my case. Instead, I would  
> like to use fast marching for reinitialization.
> Therefore I would like to repeat my question:
> Is it correct that the itkIsoContourDistanceImageFilter is a good  
> starting point?
> What is the use of the "FastMarchingExtensionImageFilter"?
>
> Thanks a lot!
>
> Best regards
> Amardeep
>
> Luis Ibanez wrote:
>>
>> Hi Amardeep
>>
>>
>> The implementation of FastMarching in ITK is initialized using
>> seed points.
>>
>> If you already have an initial front (as opposed to a set of
>> seed points) then you can use the
>>
>>              ShapeDetectionLevelSetImageFilter
>>
>> and set the curvature weight to zero. In those conditions this
>> filter will preform a front propagation similar to Fast Marching.
>>
>>
>>
>>    Regards,
>>
>>
>>       Luis
>>
>>
>>
>>
>> -------------------
>> Amardeep Singh wrote:
>>> Dear ITK-users
>>>
>>> In the current implementation of the fast marching filter, the  
>>> initial surface that is to be propagated
>>> has to be a binary interface (Please, correct me if I'm wrong).
>>> I am wondering if there is a way to apply the fast marching filter  
>>> in ITK to arbitrary inital fronts as it is described
>>> by Sethian in his paper "A fast marching level set method for  
>>> monotonically
>>> advancing fronts" (PNAS, February 1996). If such a functionality  
>>> does not exist at the moment:
>>> Would you agree that the itkIsoContourDistanceImageFilter might be  
>>> a good starting point to implement the initial
>>> calculation of the signed distances to some arbitrary isosurface?  
>>> These distances might then be used for the fast marching  
>>> propagation as described by Sethian.
>>>
>>> Thanks a lot!
>>>
>>> Best regards
>>> Amardeep
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--
Luca Antiga, PhD
Head, Medical Imaging Unit,
Biomedical Engineering Department,
Mario Negri Institute.
mail: Villa Camozzi, 24020, Ranica (BG), Italy
phone: +39 035 4535-381
email: antiga at marionegri.it
web: http://villacamozzi.marionegri.it/~luca

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