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<TITLE>RE: [Insight-users] modify transformation parameters by usingitkBSplineDeformableTransform</TITLE>
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<P><FONT SIZE=2>Xi,<BR>
<BR>
I would think that this would be easier to implement using a ThinPlateSpline Transform.<BR>
<BR>
Vince<BR>
<BR>
<BR>
----------------------<BR>
Associate Professor<BR>
Department of Radiology<BR>
0453-D JCP<BR>
200 Hawkins Drive<BR>
Iowa City, IA 52242<BR>
E-mail: vincent-magnotta@uiowa.edu<BR>
Phone: 319-356-8255 Fax: 319-353-6275<BR>
Website: <A HREF="http://www.radiology.uiowa.edu">http://www.radiology.uiowa.edu</A><BR>
<BR>
<BR>
<BR>
-----Original Message-----<BR>
From: insight-users-bounces@itk.org on behalf of Xi Liang<BR>
Sent: Sun 5/9/2010 7:50 PM<BR>
To: Luis Ibanez<BR>
Cc: insight-users@itk.org<BR>
Subject: Re: [Insight-users] modify transformation parameters by usingitkBSplineDeformableTransform<BR>
<BR>
Hi Luis,<BR>
<BR>
Thank you for the response. I think I did not make my question clear, and<BR>
the following is the purpose to write the code.<BR>
<BR>
My goal is not to create a Transform filter to be used in a registration. I<BR>
want to create a simulated motion (include nonrigid and rigid deformations).<BR>
I have a random nonrigid bspline deformation transformation parameters (can<BR>
be easily get the corresponding deformation field), and a segment mask<BR>
image. These two are my input. I want the output to be a nonrigid<BR>
deformation field. This generated deformation field will be used on a image<BR>
that has nonrigid and rigid structures, where the rigid area is the same as<BR>
the input segment mask. Therefore I need to either modify the transformation<BR>
parameters, or the corresponding deformation field to achieve a partial<BR>
rigid deformations.<BR>
<BR>
I am currently modifying a filter based on<BR>
<A HREF="http://elastix.isi.uu.nl/doxygen/a00228.html">http://elastix.isi.uu.nl/doxygen/a00228.html</A>. I am reading the ITK software<BR>
guide and try to understand how it works. The author Marius Staring told me<BR>
It can be easily modified to fill my need -- assigning a subset of a<BR>
deformation field with its mean value.<BR>
<BR>
Luis, you suggest that there are better ways to implement a Transform that<BR>
behaved as a Translation (or rigid) transformation in some regions and as<BR>
Deformable in others. What is that? Is that similar to the above method? to<BR>
modify the deformation field. Or you suggest a different scheme?<BR>
<BR>
<BR>
1) If you want to implement a Transform that behaves as<BR>
a Translation (or Rigid) transform in some regions and<BR>
as Deformable in others, there are better ways of<BR>
implementing such class, than fiddling with the parameters<BR>
of the BSplineDeformable transfrom.<BR>
<BR>
On 10 May 2010 07:50, Luis Ibanez <luis.ibanez@kitware.com> wrote:<BR>
<BR>
> Hi Xi,<BR>
><BR>
><BR>
> 1) If you want to implement a Transform that behaves as<BR>
> a Translation (or Rigid) transform in some regions and<BR>
> as Deformable in others, there are better ways of<BR>
> implementing such class, than fiddling with the parameters<BR>
> of the BSplineDeformable transfrom.<BR>
><BR>
> 2) But, just to answer your question. The parameter array<BR>
> of the BSpline transform has the components of the<BR>
> deformation vectors at every node of the BSpline grid.<BR>
><BR>
> Given a BSpline grid with N nodes in 3D, you will have<BR>
><BR>
> 3 x N parameters<BR>
><BR>
> and they are arranged as:<BR>
><BR>
> X1,X2,X3....... Xn, Y1,Y2,Y3.....YN,...Z1, Z2, Z3,... ZN<BR>
><BR>
><BR>
> 3) You can change those parameters manually.<BR>
> Simply have to figure out which BSpline nodes<BR>
> are on top of the regions for which you want to<BR>
> allow only Translations, and change those<BR>
> accordingly.<BR>
><BR>
><BR>
><BR>
><BR>
> Regards,<BR>
><BR>
><BR>
> Luis<BR>
><BR>
><BR>
><BR>
> ---------------------------------------------<BR>
> On Wed, May 5, 2010 at 6:58 AM, Xi Liang <liangxi1986317@hotmail.com><BR>
> wrote:<BR>
> > Dear all,<BR>
> > I want to change the some control point parameters got by running<BR>
> > registration by using itkBSplineDeformableTransform.h. The reason is to<BR>
> > manually modify a set of control points such that only translation is<BR>
> > applied on the corresponding regions. The question I would like to ask is<BR>
> > whether this should be done manually, or we have a filter to change those<BR>
> > parameters?<BR>
> > If I have to do this manually, I will have to understand of the format of<BR>
> > parameters. I understand the number of parameters get<BR>
> > from itkBSplineDeformableTransform is ImageDimension *<BR>
> > (numberOfGridNodesInOneDimension + BsplineOrder). Which value is for<BR>
> > lower/upper borders, and which are for nodes? I think I will only need to<BR>
> > modify the node values to enforce the translation transformations.<BR>
> > This method is introduced by Tanner in Volume and Shape Preservation of<BR>
> > Enhancing Lesions when applying nonrigid registration to a time series of<BR>
> > contrast enhancing MR breast Images. It couples the control points of a<BR>
> > bspline deformation to enforce rigidity on certain structures.<BR>
> > Kind regards,<BR>
> > Xi<BR>
> ><BR>
> ><BR>
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