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

[Luis Ibanez]

Hi Moti,

 From your description is seems that you have not initialized
the Center of rotation of the Transform.

Here are several thing that you may want to try:


1) Initialize the transform using the Centered Transform Initializer
    with the Geometry option ON.

    Please look at the ITK Software Guide for details on how to use
    this initializer. There is also a discussion on the importance
    of setting the Transform center of rotation when performing
    image registration.

          http://www.itk.org/ItkSoftwareGuide.pdf


2) Do you have a command observer connected to the optimizer ?
    If so, please post to the list the output of the observer.
    (e.g. metric values and transform parameters at every iteration.


3) Please post to the list the characteristics of your images

      a) origin in mm
      b) spacing in mm
      c) number of pixels along every dimension



The Powell optimizer is "usable" with a VersorTransform.
It is not the ideal setting, but given a judicious choice
of parameters it should be able to optimize this transform.



    Regards,


       Luis


------------------------
Moti Freiman wrote:
> 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 
> <mailto: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
>     <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
>      >
>      >
>      >
>     ------------------------------------------------------------------------
> 
>      >
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> 
> 
> 
> 
> -- 
> __
> 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