[Insight-users] ThresholdSegmentationLevelSet smoothness

[Oleksandr Dzyubak]

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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