[Insight-users] About Level sets

Mon Aug 20 14:30:43 EDT 2007

Ah ok .. now it makes complete sense. I am so pleased with the way ITK has
been designed, it is so easy to use. Thumbs up to its designers!

Thanks again Luis, 

Rashed. 

Luis Ibanez wrote:
> 
> 
> Hi Rashed,
> 
> The speed image is a grayscale image, typically with pixel
> values in the range from 0.0 to 1.0.  The image must have
> values 0.0 in the places where you want the LevelSet front
> to stop, and should have values close to 1.0 in the places
> where you want to levelset front to propagate.
> 
> You will find multiple examples of how a good speed image
> should look like in the ITK Software Guide:
> 
> 
>        http://www.itk.org/ItkSoftwareGuide.pdf
> 
> 
> See for example, section 9.3.1 "Fast Marching Segmentation",
> in pdf-pages 565-573. You will see examples of speed images
> in figures 9.16, 9.18 and 9.22. All of these illustrate
> speed images based on the gradient magnitude.
> 
> 
> 
>      Regards,
> 
> 
>         Luis
> 
> 
> 
> -------------------
> rashedk wrote:
>> Thanks for your reply Luis, and I am glad to know that this is possible
>> using
>> ITK. 
>> 
>> But I dont understand what I need to put into this *speed image*. Is this
>> a
>> binary image or grey-scale? Can you give me an example of what a speed
>> image
>> would contain if the propagating front speed was governed by the image's
>> intensity gradient magnitude?  
>> 
>> Thanks for your reply, I really appreciate. 
>> 
>> Regards,
>> Rashed karim 
>> 
>> 
>> 
>> Luis Ibanez wrote:
>> 
>>>
>>>Hi Rashed,
>>>
>>>                     Yes, it is possible.
>>>
>>>
>>>Note that, for example, in FastMarching, *you* build the
>>>speed image. Therefore, you can simply precompute the images:
>>>
>>>    a) Gradient magnitude
>>>    b) Vesselness
>>>
>>>and combine them in any way you want to generate the speed image.
>>>It seems, for example, that a multiplication of the two images will
>>>produce the "AND" effect that you are looking for.
>>>
>>>
>>>Then, finally, pass the computed speed image to the FastMarching
>>>filter, as you have already seen it described in the ITK Software
>>>Guide.
>>>
>>>
>>>If you want to make a more sophisticated mixture of terms,
>>>then you can easily write your own LevelSet filter, by still
>>>reusing the ITK framework. In this case, you have to write
>>>two classes:  X_LevelSetImageFunction and X_LevelSetImageFilter.
>>>In this scenario, you will find useful to look at the code
>>>implementing other LevelSet filters.
>>>
>>>
>>>Also, since you are interested in Vessel segmentation, you may
>>>find useful the following paper posted in the Insight Journal:
>>>
>>>
>>>"Generalizing vesselness with respect to dimensionality and shape"
>>>by Antiga, Luca
>>>http://www.insight-journal.org/InsightJournalManager/view_reviews.php?back=search.php%3Ftexte%3Dvessel&journalid=9&pubid=175
>>>
>>>	
>>>"Vessel Enhancing Diffusion Filter"
>>>Enquobahrie, Andinet; Ibanez, Luis; Bullitt, Elizabeth; Aylward, Stephen
>>>http://www.insight-journal.org/InsightJournalManager/view_reviews.php?back=search.php%3Ftexte%3Dvessel&journalid=8&pubid=163
>>>
>>>
>>>
>>>If you find these papers useful, you are strongly encouraged to
>>>support OPEN ACCESS by posting reviews to the papers. Please note
>>>that the reviews of the Insight Journal are not intended to be the
>>>empty reviews of decadent traditional journals where the reviewers
>>>simply speculate on what "they think" about the paper. On the contrary
>>>the Insight Journal expects comments from fellow developers of image
>>>analysis software who *actually* compiled and run the source code that
>>>is accompanying the paper, and report on their experience on the use
>>>of the code.
>>>
>>>
>>>
>>>    Peer-review without reproducibility is mindless babbling.
>>>
>>>    We already have had enough of that in our field...
>>>    It is time to raise from the muddy waters of narcissism
>>>    and move our field up to the standards of scientific work.
>>>
>>>
>>>
>>>By the same token, If you find a way of integrating the two images
>>>as input to your level set filter, you are also *strongly encouraged*
>>>to submit your work as a paper to the Insight Journal. Here again,
>>>papers to the Insight Journal are not about the childish quest for
>>>"originality" claims that disgustingly plague the decadent journals
>>>of our field. Instead, we expect your paper to demonstrate that the
>>>practical solution that you found to your real image processing
>>>problem, actually works. The demonstration is provided not by textual
>>>arguments in your paper, but by the source code, parameters, images,
>>>and instructions that you provide, describing how to *REPRODUCE* your
>>>tests.
>>>
>>>
>>>  Please let us know if you have any further questions,
>>>
>>>
>>>     Thanks
>>>
>>>
>>>        Luis
>>>
>>>
>>>
>>>------------------
>>>rashed karim wrote:
>>>
>>>>Hi Everyone,
>>>>
>>>>Is it possible to use the ITK level set implementations (such as Fast 
>>>>marching, Geodesic, Laplacian, etc.) to drive a propogating front whose 
>>>>speeds are governed by let's say two factors: 1. Gradient magnitude 2. 
>>>>Frangi's vesselness. I want the propagating front to stop speeding at 
>>>>points which give high responses to the vesselness filter AND have high 
>>>>image gradient magnitudes.
>>>>
>>>>Does ITK level set implementations allow users to define their own 
>>>>criterion which limits the speed of the active contour? I have had a 
>>>>good look at the ITK software guide, and it seemed like this isn't 
>>>>possible.
>>>>
>>>>Thanks in advance,
>>>>
>>>>Regards,
>>>>Rashed Karim
>>>>
>>>>
>>>>------------------------------------------------------------------------
>>>>
>>>>_______________________________________________
>>>>Insight-users mailing list
>>>>Insight-users at itk.org
>>>>http://www.itk.org/mailman/listinfo/insight-users
>>>
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>>>
>> 
>> 
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