[Insight-users] muliple pahse Chan Vese, one partition totally shrink

[Kishore Mosaliganti]

Hi Baoyun,

You are right that if you set 4 phases in the levelset, then no phase will
shrink to empty.

In ITK, if you use the classes on ScalarChanAndVeseLevelSetImageFilter, you
can separately encode the 3 regions in 3 separate level-set functions and
these functions compete with each other for the segmentations at the
boundaries. You can also control each level-set parameters separately.

If you have N objects, then you can make use of a built-in kd-tree
optimization that speeds up the approach. Each levelset function is only
defined in a small subdomain containing your object instead of the whole
image thereby saving space.


Kishore

On Fri, Mar 26, 2010 at 10:48 AM, Baoyun Li <baoyun_li123 at yahoo.com> wrote:

> Dear All:
>
> Thanks for your reply, now seems I undertand the question more.
>
> According to Wanlin's paper, I need to encoding the 2 level set to  3 phase
> if I want to 3 segmenations. If I need 4  segmentation, I need to encode the
> levelset to 4 phases.
>
> So my origianl question is not correct, once I set 4 phases, no phase will
> shrink to empty, and I will get 4 segmentation anyway. (Please correct me if
> I am wrong).
>
> Thanks and my best regards
>
> Baoyun
>
> Please correct me if I am wrong
>
> --- On *Thu, 3/25/10, Luis Ibanez <luis.ibanez at kitware.com>* wrote:
>
>
> From: Luis Ibanez <luis.ibanez at kitware.com>
>
> Subject: Re: [Insight-users] muliple pahse Chan Vese, one partition totally
> shrink
> To: "Baoyun Li" <baoyun_li123 at yahoo.com>
> Cc: insight-users at itk.org, "Mosaliganti, Kishore Rao" <
> Kishore_Mosaliganti at hms.harvard.edu>
> Date: Thursday, March 25, 2010, 10:43 PM
>
>
>
> Hi Baoyun,
>
>
> You seem to be mixing two different issues here.
>
> One thing is to segment the image in different regions,
> and a separate issue is to find an efficient encoding
> for the resulting segmentations.
>
>
> If you want to segment three different anatomical structures
> from your image, then you want to use a level set with
> three phases.
>
> That is, one phase per object to be segmented.
>
>
>       Regards,
>
>
>             Luis
>
>
>
> -----------------------------------------------------------------------------
> On Wed, Mar 24, 2010 at 5:52 PM, Baoyun Li <baoyun_li123 at yahoo.com<http://us.mc1110.mail.yahoo.com/mc/compose?to=baoyun_li123@yahoo.com>
> > wrote:
>
>>   Dear All:
>>
>> I have a theoritical question about Chen Vese multiplse pahse leve set.
>>
>> I have two level set and the two level set can segment the image to 4
>> segments, then I can calculate the mean for each segments as following
>>
>> %c11 = mean (phi1>0 & phi2>0)
>> %c12 = mean (phi1>0 & phi2<0)
>> %c21 = mean (phi1<0 & phi2>0)
>> %c22 = mean (phi1<0 & phi2<0)
>>
>> How about if I only have three segments, let say segment (phi1<0 & phi2<0)
>> will finally shrink to zeros.
>>
>> Then how to I calcuate c22, and also what value of c22 I should use
>> to update leve set equation as shown below:
>>
>> ((u-c22)^2-(u-c12)^2)H(phi2).
>>
>> I saw somebody use the mininum number of the machine to replace c22, but I
>> could not imagine what will happen and why to do that.
>>
>> Thanks
>> Baoyun
>>
>>
>>
>>
>>
>>
>>
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> http://www.kitware.com/products/protraining.html
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