[Insight-users] non-gradient base optimizer for 3D registration with versors

[Moti Freiman]

Hi Luis,
Thanks for your quick response.

1. I assumed that i have a bad setting of the parameters, but I've no idea
from where to start.
My images are T2 mri images which were taken in two times. Firstly i used
the mutual information multi resolution example provided with the ITK to
register them. I initialized the transform with the identity transform. and
the images registered well.
Then I started to modify the multi resolution example to working with my
similarity measure.
The first step was to use the Powell optimizer instead of the versor
optimizer , but staying with the 3d rigid versor transform, and
initialization to the identity transform. In the first evaluation of the
similarity measure i got the exception. The scaling parameters and others
were the same as appear in the multi resolution MI registration example.
I also tried to change the similarity measure from MI to my similarity
measure, but after 4 evaluations, i got  the exception when it starts to
apply the rotation about the Z axiz.

2. Is the powell optimizer can work with the versor transform, or just with
euler3D transform ?
3. Is there anywhere  example of 3D registration with the powell optimizer?

Many thanks,
Moti

On 4/15/07, Luis Ibanez <luis.ibanez at kitware.com> wrote:
>
>
> Hi Moti,
>
>
> Here are a couple of suggestions:
>
>
> 1) You can use the OnePlusOne evolutionary optimizer.
>     This optimizer does not require gradients in the
>     cost function. Note that the versor rigid 3D transform
>     will map its parameters to the Versor space, so that
>     you stay in the unit sphere.
>
>
>
>
>     but.. before you get rid of the Powell optimizer,
>     note that you may be simply using a bad set of
>     parameters for it:
>
>
>
> 2) The message that you are getting from the Powell optimizer
>     can be related to:
>
>       A) Poor initialization of the transform.
>
>          How are you initializing your transform ?
>          Have you verified that the initial transform
>          give you a large overlap of the fixed and moving images ?
>
>
>       B) Using steps that are too large
>
>          How many iterations does the optimizer performs before
>          you get the exception ?
>          What parameters are you passing to the optimizer
>
>
>
>       C) Lack of using a right combination of parameter scaling.
>
>          What values are you setting for the parameter scaling?
>          This is very important, since it compensates for the
>          difference in the dynamic range of the versor components
>          versus the translation components.
>          You may find useful to read the description of this
>          issue in the ITK Software Guide:
>
>              http://www.itk.org/ItkSoftwareGuide.pdf
>
>
>
>
>     Regards,
>
>
>         Luis
>
>
> ---------------------
> Moti Freiman wrote:
> > Hello,
> > I'm trying register two 3D volumes within the ITK framework using a new
> > similarity measure which has no analytical gradients.
> > Since the 3D versor optimizer in itk is based on a gradient decent
> > optimizer. i cannot use it with my similarity measure.
> > I tried to use the Powell optimizer with 3DRigidVersor transform but I
> > got the following message:
> > "All the points mapped to outside of the moving image"
> > It seems that powell is not optimized for the versor space.
> > 1. Is there any option to build a non-gradient based optimizer for the
> > versor space as it done for gradient decent optimizer?
> > 2. Any other suggestions to which elements i should use in my
> > registration process given that my similarity measure has no gradients?
> > Thanks,
> > Moti
> > --
> > __
> > Moti Freiman, Ph.D Student.
> > Medical Image Processing and Computer-Assisted Surgery Laboratory.
> > School of Computer Science and Engineering.
> > The Hebrew University of Jerusalem Givat Ram, Jerusalem 91904, Israel
> > Phone: +(972)-2-658-5371 (laboratory)
> > WWW site: http://www.cs.huji.ac.il/~freiman
> > <http://www.cs.huji.ac.il/%7Efreiman>
> >
> > --
> > __
> > Moti Freiman, Ph.D Student.
> > Medical Image Processing and Computer-Assisted Surgery Laboratory.
> > School of Computer Science and Engineering.
> > The Hebrew University of Jerusalem Givat Ram, Jerusalem 91904, Israel
> > Phone: +(972)-2-658-5371 (laboratory)
> > WWW site: http://www.cs.huji.ac.il/~freiman
> >
> >
> > ------------------------------------------------------------------------
> >
> > _______________________________________________
> > Insight-users mailing list
> > Insight-users at itk.org
> > http://www.itk.org/mailman/listinfo/insight-users
>



-- 
__
Moti Freiman, Ph.D Student.
Medical Image Processing and Computer-Assisted Surgery Laboratory.
School of Computer Science and Engineering.
The Hebrew University of Jerusalem Givat Ram, Jerusalem 91904, Israel
Phone: +(972)-2-658-5371 (laboratory)
WWW site: http://www.cs.huji.ac.il/~freiman
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