Hi Luis,<br>Thanks for your quick response.<br><br>1. I assumed that i have a bad setting of the parameters, but I've no idea from where to start.<br>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.
<br>Then I started to modify the multi resolution example to working with my similarity measure.<br>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.
<br>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.<br><br>2. Is the powell optimizer can work with the versor transform, or just with euler3D transform ?
<br>3. Is there anywhere example of 3D registration with the powell optimizer?<br><br>Many thanks,<br>Moti <br><br><div><span class="gmail_quote">On 4/15/07, <b class="gmail_sendername">Luis Ibanez</b> <<a href="mailto:luis.ibanez@kitware.com">
luis.ibanez@kitware.com</a>> wrote:</span><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"><br>Hi Moti,<br><br><br>Here are a couple of suggestions:
<br><br><br>1) You can use the OnePlusOne evolutionary optimizer.<br> This optimizer does not require gradients in the<br> cost function. Note that the versor rigid 3D transform<br> will map its parameters to the Versor space, so that
<br> you stay in the unit sphere.<br><br><br><br><br> but.. before you get rid of the Powell optimizer,<br> note that you may be simply using a bad set of<br> parameters for it:<br><br><br><br>2) The message that you are getting from the Powell optimizer
<br> can be related to:<br><br> A) Poor initialization of the transform.<br><br> How are you initializing your transform ?<br> Have you verified that the initial transform<br> give you a large overlap of the fixed and moving images ?
<br><br><br> B) Using steps that are too large<br><br> How many iterations does the optimizer performs before<br> you get the exception ?<br> What parameters are you passing to the optimizer<br>
<br><br><br> C) Lack of using a right combination of parameter scaling.<br><br> What values are you setting for the parameter scaling?<br> This is very important, since it compensates for the<br> difference in the dynamic range of the versor components
<br> versus the translation components.<br> You may find useful to read the description of this<br> issue in the ITK Software Guide:<br><br> <a href="http://www.itk.org/ItkSoftwareGuide.pdf">
http://www.itk.org/ItkSoftwareGuide.pdf</a><br><br><br><br><br> Regards,<br><br><br> Luis<br><br><br>---------------------<br>Moti Freiman wrote:<br>> Hello,<br>> I'm trying register two 3D volumes within the ITK framework using a new
<br>> similarity measure which has no analytical gradients.<br>> Since the 3D versor optimizer in itk is based on a gradient decent<br>> optimizer. i cannot use it with my similarity measure.<br>> I tried to use the Powell optimizer with 3DRigidVersor transform but I
<br>> got the following message:<br>> "All the points mapped to outside of the moving image"<br>> It seems that powell is not optimized for the versor space.<br>> 1. Is there any option to build a non-gradient based optimizer for the
<br>> versor space as it done for gradient decent optimizer?<br>> 2. Any other suggestions to which elements i should use in my<br>> registration process given that my similarity measure has no gradients?<br>> Thanks,
<br>> Moti<br>> --<br>> __<br>> Moti Freiman, Ph.D Student.<br>> Medical Image Processing and Computer-Assisted Surgery Laboratory.<br>> School of Computer Science and Engineering.<br>> The Hebrew University of Jerusalem Givat Ram, Jerusalem 91904, Israel
<br>> Phone: +(972)-2-658-5371 (laboratory)<br>> WWW site: <a href="http://www.cs.huji.ac.il/~freiman">http://www.cs.huji.ac.il/~freiman</a><br>> <<a href="http://www.cs.huji.ac.il/%7Efreiman">http://www.cs.huji.ac.il/%7Efreiman
</a>><br>><br>> --<br>> __<br>> Moti Freiman, Ph.D Student.<br>> Medical Image Processing and Computer-Assisted Surgery Laboratory.<br>> School of Computer Science and Engineering.<br>> The Hebrew University of Jerusalem Givat Ram, Jerusalem 91904, Israel
<br>> Phone: +(972)-2-658-5371 (laboratory)<br>> WWW site: <a href="http://www.cs.huji.ac.il/~freiman">http://www.cs.huji.ac.il/~freiman</a><br>><br>><br>> ------------------------------------------------------------------------
<br>><br>> _______________________________________________<br>> Insight-users mailing list<br>> <a href="mailto:Insight-users@itk.org">Insight-users@itk.org</a><br>> <a href="http://www.itk.org/mailman/listinfo/insight-users">
http://www.itk.org/mailman/listinfo/insight-users</a><br></blockquote></div><br><br clear="all"><br>-- <br>__<br>Moti Freiman, Ph.D Student.<br>Medical Image Processing and Computer-Assisted Surgery Laboratory.<br>School of Computer Science and Engineering.
<br>The Hebrew University of Jerusalem Givat Ram, Jerusalem 91904, Israel<br>Phone: +(972)-2-658-5371 (laboratory)<br>WWW site: <a href="http://www.cs.huji.ac.il/~freiman">http://www.cs.huji.ac.il/~freiman</a>