[Insight-users] Demons Registration

[Tom Vercauteren]

Hi Ganesh,

On Wed, Feb 23, 2011 at 19:04, Ganesh Narayanasamy
<nganesh76 at hotmail.com> wrote:
>
> When I run DemonsRegistration using the options as given in the command line
> below, I can get a few output files like final image, deformation field etc.
> How would I get the rest of the output like "True field file"?

 The "true field" is an input not an output. It may be used for
synthetic experiments where the actual deformation is known.
DemonsRegistration then compares at each iteration its result against
this ground truth (but of course it does not use it to drive the
registration).


> As the image was not deforming enough, I had opted to reduce sigma from the
> default value of 1.5 to 0.8.. is this the correct approach?

This entirely depends on your use case... That being said, I would
first try to use more iterations and then reduce the sigma.


> Size of the fixed and moving images are 384x384x64 pixels each. I would like
> to register using the multi-resolution approach starting with 1/4th number
> of pixels in all 3 axes (i.e, 96x96x16), going to 1/2 (ie., 192x192x32
> pixels) and finally to the full image. How will I do this?

It is already done, see the number of multiresolution levels and
number of iterations per level:
>   Number of multiresolution levels: 3
>   Number of demons iterations: [ 15 10 5 ]

Hope this helps,
Tom


> Command:
>>DemonsRegistration.exe -f CBCT1.mha -m CBCT4.mha -o Final.mha -O DefFld.mha
>> -s 0.8 -d 1
>
> Starting demons registration with the following arguments:
> Arguments structure:
>   Fixed image file: CBCT1.mha
>   Moving image file: CBCT4.mha
>   Input field file:
>   Input transform file:
>   Output image file: Final.mha
>   Output field file: DefFld.mha
>   True field file:
>   Number of multiresolution levels: 3
>   Number of demons iterations: [ 15 10 5 ]
>   Deformation field sigma: 0.8
>   Update field sigma: 0
>   Maximum update step length: 2
>   Update rule: exponentialize and compose (Diffeomorphic)
>   Type of gradient: symmetrized (ESM for diffeomorphic and compositive)
>   Use histogram matching: false
>   Algorithm verbosity (debug level): 1
>
> Thanks,
> Ganesh