[Insight-users] Segmenting Visible Human Data

[Luis Ibanez]

Hi Stefan,


The reason for postprocessing the joint regions is that
if you take two contiguous pieces of the image and run
level sets on each one, the level sets will evolve in
a different way at each side of the boundary, and it
is likely that if you try to put the two level sets
together just by joining the two blocks of data, the
zero set surface will not be contiguous from one block
to the next.

I would anticipate that some smoothing will be needed
for ironing out any discontinuity in the connection.
taking the joint region (a region around the boundary
of the two block and running some more iterations of
the level set there may help to smooth out the transition
between the blocks.

You could certainly attempt this post-processing-smoothing
with other methods. For example, a simple median filter
has proved to be powerful enough for smoothing out
transitions and it will be a much faster approach too.

You may want to start by trying Josh's suggestion since
he and his group are the ones who experimented more
deeply into this issue.


Please let of know of your findings,


  Thanks


   Luis


-----------------------
Stefan Lindenau wrote:
> Hi Luis,
> 
> thank you for your quick and comprehensive answer. I will just have to 
> cut the image in pieces.
> 
> Only one thing I still do not understand:
> 
>> If you use level sets, you could post process
>> the joint regions between your contiguous pieces
>> in order to smooth out the potential differences
>> between the level set obtained in one region and
>> the level set obtained in the facing region.
> 
> 
> Why is it dependend on the level sets to postprocess the the joint 
> region. In my comprehension I will just cut the data in big 
> pieces,process it and put it together just after the processing. Then 
> such a postprocessing should be possible with any of the methods. Or did 
> I ignore some facts?
> 
> Maybe I can get it working with the streaming example for watershed 
> algorithms as Joshua proposed. I will just have to test it out.
> 
> 
> thanks
> Stefan
> 
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