<DIV>
<DIV>Hi Luis,</DIV>
<DIV> </DIV>
<DIV>Thank you!</DIV>
<DIV> </DIV>
<DIV>In SPM, the equations to transform the moving image is as follows</DIV>
<DIV><FONT color=#00007f>x1=R00*x+R01*y+R02*z+Trans0</FONT></DIV>
<DIV><FONT color=#00007f>y1=R10*x+R11*y+R12*z+Trans1</FONT></DIV>
<DIV><FONT color=#00007f>z1=R20*x+R21*y+R22*z+Trans2</FONT></DIV>
<DIV> </DIV>
<DIV>But SPM integrates spacing info into the rotation 3X3 matrix.</DIV>
<DIV> </DIV>
<DIV>I compared the result from ITK and the one from SPM, </DIV>
<DIV><FONT color=#00407f><FONT color=#000000>I found</FONT> ITKrotation*ITKspacing</FONT> is very close to the <FONT color=#00007f>Ratation</FONT> matrix in SPM and the translations are also very close.</DIV>
<DIV> </DIV>
<DIV>But I can not obtain a good transform in SPM using ITK result.</DIV>
<DIV>Do you think there will be other reasons for this? like the interpolation method (default setting in SPM is linear and I use linear in ITK)?</DIV>
<DIV> </DIV>
<DIV>Best regards,</DIV>
<DIV>Yu Qi</DIV>
<DIV><BR><BR><B><I>Luis Ibanez <luis.ibanez@kitware.com></I></B> дµÀ£º</DIV>
<BLOCKQUOTE class=replbq style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #1010ff 2px solid"><BR>Hi Yu,<BR><BR>I'm not familiar enough with SPM to give you a good advice here.<BR><BR>But in general the part that needs to be transposed is just the<BR>3x3 Matrix containing the rotational part of the transform.<BR><BR>This may or may not be enough for SPM, you may end up needing a<BR>full 4x4 transpose.<BR><BR>Note that you don't necessarily need to transpose the transform.<BR>This is only if you find that the representation of the transform<BR>in ITK uses a different standard from the one present in SPM.<BR><BR><BR>Sorry for not being of much help in this issue,<BR><BR><BR>Luis<BR><BR><BR><BR>--------------------------------------------------------------<BR>Yu Qi wrote:<BR><BR>> Hi Luis,<BR>> <BR>> I am also trying to export the transform in ITK to other applications, <BR>> but to SPM rather tan VTK.<BR>> <BR>> One question I want to ask is<BR>> can I
simply use the a 4X4 matrix as follows to transform a image?<BR>> | last translationX |<BR>> | GetRotationMatrix 3X3 last translationY |<BR>> | last translationZ |<BR>> | 0 0 0 1 |<BR>> <BR>> and you mentioned transpose, why do we need transpose?<BR>> <BR>> <BR>> Thank you!<BR>> Best regards,<BR>> Yu Qi<BR>> <BR>> <BR>> */Luis Ibanez <LUIS.IBANEZ@KITWARE.COM>/* дµÀ£º<BR>> <BR>> <BR>> Hi Toon,<BR>> <BR>> <BR>> What you are doing seems to be reasonable.<BR>> <BR>> The only thing that can be wrong in your process is<BR>> that the Matrix may need to be transposed.<BR>> <BR>> <BR>> However, before we go there, could you please<BR>> share with us the evidence that lead you to think<BR>> that the transformation is not correct ?<BR>> <BR>> <BR>> If you are obtaining the Versor transform as the<BR>> result of an image registration process in ITK,<BR>> chances are that you are being confused by
the<BR>> direction in which Transforms are computed in ITK.<BR>> <BR>> <BR>> Please let us know,<BR>> <BR>> <BR>> Thanks<BR>> <BR>> <BR>> Luis<BR>> <BR>> <BR>> -------------------<BR>> Toon Huysmans wrote:<BR>> <BR>> > Hi,<BR>> ><BR>> ><BR>> ><BR>> > I have registered two images and I have the result in a<BR>> > VersorRigid3DTransform, now I would like to transform some<BR>> vtkPolyData<BR>> > using this transform. I believe! that VersorRigid3DTransform<BR>> contains a<BR>> > rotation (the versor) and a translation, so I set up a 4x4 matrix,<BR>> > containing the rotation and translation as follows:<BR>> ><BR>> > | R11 R12 R13 Tx |<BR>> ><BR>> > | R21 R22 R23 Ty |<BR>> ><BR>> > | R31 R32 R33 Tz |<BR>> ><BR>> > | 0 0 0 1 |<BR>> ><BR>> ><BR>> ><BR>> > I get the rotation matrix R using<BR>> >
VersorRigid3DTransform::GetRotationMatrix<BR>> > ,<BR>> > and the translation part using VersorRigid3DTransform::GetOffset<BR>> > .<BR>> > Then I use vtkTransform::SetMatrix to set the transform for the<BR>> > polydata, and I use<BR>> ><BR>> > vtkTransformPolyDataFilter to transform the polydata. But the<BR>> resul! t is<BR>> > not as expected, i.e. the transformation is not correct.<BR>> ><BR>> ><BR>> ><BR>> > Does anyone have any clues on how to do it the right way?<BR>> ><BR>> ><BR>> ><BR>> > Many thanks,<BR>> ><BR>> ><BR>> ><BR>> > Toon Huysmans.<BR>> ><BR>> ><BR>> ><BR>> ><BR>> ><BR>> > ¥ ?lt;br>><BR>> > ?Postal Address: ?lt;br>><BR>> > ? ?lt;br>><BR>> > ?Vision Lab, Department of Physics ?lt;br>><BR>> > ?University of
Antwerp (CMI) ?lt;br>><BR>> > ?Groenenborgerlaan 171 (U306) ?lt;br>><BR>> > ?B-2020 Antwerp, Belgium ?lt;br>><BR>> > °€EUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUR?lt;br>><BR>> > ?Tel: +32 (0) 3 265 32 24 ?lt;br>><BR>> > °€EUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUR?lt;br>><BR>> > ?Fax: +32 (0) 3 265 33 18 ?lt;br>><BR>> > °€EUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUR?lt;br&g! t;><BR>> > ?Email: toon.huysmans@ua.ac.be<BR>> > ?lt;br>><BR>> >
°€EUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUREUR?lt;br>><BR>> > ?Web: http://webhost.ua.ac.be/visielab/staff/tohu/ ?lt;br>><BR>> > « ?lt;br>><BR>> ><BR>> ><BR>> ><BR>> ><BR>> ------------------------------------------------------------------------<BR>> ><BR>> > _______________________________________________<BR>> > Insight-users mailing list<BR>> > Insight-users@itk.org<BR>> > http://www.itk.org/mailman/listinfo/insight-users<BR>> <BR>> <BR>> <BR>> _______________________________________________<BR>> Insight-users mailing list<BR>> Insight-users@itk.org<BR>> http://www.itk.org/mailman/listinfo/insight-users<BR>> <BR>> <BR>> ------------------------------------------------------------------------<BR>> *Do
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