[Insight-users] ThresholdSegmentationLevelSet smoothness

[Luis Ibanez]

Hi Oleksandr

    Can you share with us what you
    are referring to by using F(x) and K(x)  ?

    That will be nice   :-)


       Thanks


          Luis



-----------------------------
Oleksandr Dzyubak wrote:
> Hi Luis,
> 
> Keeping PropagationScaling=1.0, I varied CurvatueScaling over the range 
> [1-1000].
> As you said, there is a smoothing effect but not as much as I expected
> and the cylinder is still a cylinder.
> What approach did you use?
> 
> a) F(a + b)=1
> b) F(a) + K(b)=1
> c) F(a*b)->[0-1]
> d) F(a) ->[0-1] AND K(b) ->[0-1]
> e) something else?
> 
> If b) is the case, then setting PropagationScaling << 1.0 should have
> a smoothing effect as well (or even stronger?), right? For the cost of 
> sensitivity loss I believe, right?
> How did you normalize the parameters
> that such a large CurvatueScaling range is still acceptable?
> 
> Concerning the ends your are right. I should have used the padding.
> 
> Regards,
> 
> Alex
> 
> Luis Ibanez wrote:
> 
>>
>> Hi Oleksandr,
>>
>> In order to have the curvature weight parameter to have a significant
>> effect on the level set you have to set it up to a value that is around
>> 100X the one of the propagation weight. These values are relative (they
>> get normalized inside the filter), so their absolute values do not
>> matter as much as their relative values. Try pushing it to 200 times
>> the value of the propagation weight... or even higher.
>>
>> If you get a rounded sphere as segmentation...
>> then you will know that you have gone too far :-)
>>
>>
>> About the first and last slice....
>> Well, how many empty slices are between the end of the cylinder and
>> the end of the image ?
>>
>> You may have to add some padding slices with the PadImageFilter...
>>
>>
>>   Regards,
>>
>>
>>     Luis
>>
>>
>> ------------------------
>> Oleksandr Dzyubak wrote:
>>
>>>
>>> Dear Luis and ITK users,
>>>
>>> I tried to use the ThresholdSegmentationLevelSet image filter
>>> to segment an elongated gaussian cylinder. The segmentation went fine
>>> but I still have couple questions.
>>>
>>> 1)
>>> In the segmented cylinder, its edges are too rough with a bunch of 
>>> spikes.
>>> According to the user manual, the CurvatureScaling parameter could be 
>>> used
>>> as a smoother but it did not help much even if I vary it over a quite 
>>> wide range [1-100].
>>> Any suggestions on how to get the segmented object with smooth edges?
>>> What other control parameters could be used for that?
>>>
>>> 2)
>>> In the segmented image, the first and last slices of the cylinder are 
>>> excluded.
>>> It looks like propagation gets stuck at the ends.
>>> Any suggestions on how to enforce it to process the whole object?
>>>
>>> Thanks,
>>>
>>> Alex
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> 
>