[Insight-users] Question about Diffeomorphic Registration

[Kaveh Kohan]

Hi Everybody,

I am a newbie to ITK community. I have couple of questions and I would be thankful if anybody answers:

-
Is there any fluid registration method implemented in ITK, either LDDMM
(Prof. Miller et al.) or fast diffeomorphism (Prof. Ashburner) ? If
not, is there any plan to implement such methods?

- As far as I know (so far) this paper and corresponding code is the only diffeomorphic registration method implemented in ITK:

"Diffeomorphic Demons Using ITK's Finite Difference Solver Hierarchy" 
by: Tom Vercauteren, Xavier Pennec, Aymeric Perchant, Nicholas Ayache
Jun-2007

I
found it very interesting and tried it over traditional "C" example
which is commonly used as a bench mark for fluid methods. My
understanding is that this is not a large deformation method. I got
following results after trying many parameters and different update
strategies:

Fixed image:
http://www.4shared.com/file/55079305/f6267afa/fixed.html
Moving Image:
http://www.4shared.com/file/55079348/ecfbc343/moving.html

--------------------
Diffeomorphic Demon update:
.../DemonsRegistration -f fixed.nii -m moving.mha -a 0 -o Out_Diff.mha -v -i 200x4x4 -l6
Result: 
http://www.4shared.com/file/55082051/db2be42f/Out_Diff.html
------------------
Basic ITK Update:
 ../DemonsRegistration -f fixed.nii -m moving.mha -a 1 -o Out_ITK.mha -v -i 300x30x30 -l 5
Result:
http://www.4shared.com/file/55082650/a8a1a80b/Out_ITK.html
-------------------
Thirion Update:
.../DemonsRegistration -f fixed.nii -m moving.mha -a 2 -o Out_Thr.mha -v -i 300x30x30 -l 10
Result:
http://www.4shared.com/file/55080214/66a0c941/Out_Thr.html

to see warped grids and determinant of Jacobians for each method, please visit:
http://www.4shared.com/dir/8238152/7295688e/Registration_Results.html

Unlike basic ITK which produce negative Jacobian (but good registration), both Diff. Demon and Thirion methods yiled
non-negative Jacobian. However, Thirion got much better registration
result with lower residual than Diff. Demon. In addition, no matter how
small step size is, in the Multi-resolution 1 and 2 (in Diff. Demon) it
increases MSE instead of decreasing it. I know that the step size I
used for Diff. Demon is very aggresive but even with default step size
it increases MSE in the Multi-res 1& 2. 

I was wondering whether I am making a mistake or in general Thirion
update works better while procuding diffeomorphic transformation? I
mean, I think the advange of Diff. Demon is that it gaurantees to
produce Diffeomorphic transformation but does it necessarily sacrify accuracy?
or I am making a mistake somewhere? Do you think that combined method (sometimes Thirion sometimes Diff.
Demon) works better? Or this method is not essentially proper for large
deformation?

Any comment is appreciated.

Sincerely,
Kaveh


      
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