Hello, I was wondering how to use the direction cosines in DICOM when contructing a direction/rotation matrix. Should the six numbers in tag 0020|0037 represent the first two columns or the first two rows of the matrix? An ITK bug report suggests (i think) that they are the first two row vectors: http://www.cmake.org/Bug/view.php?id=7748 ...but some nifti documentation seem to state the opposite (down the bottom of the page): http://nifti.nimh.nih.gov/nifti-1/documentation/nifti1fields/nifti1fields_pages/quatern.html A short educational pdf-document implies they are the row vectors of the matrix: http://www.ae.uiuc.edu/~tbretl/ae403/handouts/06-dcm.pdf ...but wikipedia seems to state that they should be interpreted as the column vectors of the matrix: http://en.wikipedia.org/wiki/Rotation_representation_(mathematics)#Rotation_matrix_.28or_direction_cosine_matrix.2C_DCM.29 Can someone de-confuse me?! Thanks in advance, //Patrik -- View this message in context: http://old.nabble.com/Confusion-with-direction-cosines-in-DICOM%2C-tag-0020%7C0037-tp26825252p26825252.html Sent from the ITK - Users mailing list archive at Nabble.com. _____________________________________ Powered by www.kitware.com Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html Kitware offers ITK Training Courses, for more information visit: http://www.kitware.com/products/protraining.html Please keep messages on-topic and check the ITK FAQ at: http://www.itk.org/Wiki/ITK_FAQ Follow this link to subscribe/unsubscribe: http://www.itk.org/mailman/listinfo/insight-users |
Hi Patrik,
The direction cosine triplets from the DICOM header are stored in the Columns of the ITK Direction matrix. See lines: 190-203 of the file Insight/Code/IO/itkImageFileReader.txx and lines 1171-1183 of the file: Insight/Code/IO/itkGDCMImageIO.cxx The DICOM header only carry the first two direction cosine vectors. The third one is computed by ITK as the cross product of the first two. WARNING: Before you get too focuses on row versus column matrix notation, please note that ITK represent Geometrical vectors as column-vectors in a Matrix. Regards, Luis ---------------------------------------------------------------------------- On Thu, Dec 17, 2009 at 4:22 AM, Patrik.Br. <[hidden email]> wrote: > > Hello, > > I was wondering how to use the direction cosines in DICOM when contructing a > direction/rotation matrix. Should the six numbers in tag 0020|0037 represent > the first two columns or the first two rows of the matrix? > > An ITK bug report suggests (i think) that they are the first two row > vectors: > http://www.cmake.org/Bug/view.php?id=7748 > > ...but some nifti documentation seem to state the opposite (down the bottom > of the page): > http://nifti.nimh.nih.gov/nifti-1/documentation/nifti1fields/nifti1fields_pages/quatern.html > > A short educational pdf-document implies they are the row vectors of the > matrix: > http://www.ae.uiuc.edu/~tbretl/ae403/handouts/06-dcm.pdf > > ...but wikipedia seems to state that they should be interpreted as the > column vectors of the matrix: > http://en.wikipedia.org/wiki/Rotation_representation_(mathematics)#Rotation_matrix_.28or_direction_cosine_matrix.2C_DCM.29 > > Can someone de-confuse me?! > > Thanks in advance, > > //Patrik > -- > View this message in context: http://old.nabble.com/Confusion-with-direction-cosines-in-DICOM%2C-tag-0020%7C0037-tp26825252p26825252.html > Sent from the ITK - Users mailing list archive at Nabble.com. > > _____________________________________ > Powered by www.kitware.com > > Visit other Kitware open-source projects at > http://www.kitware.com/opensource/opensource.html > > Kitware offers ITK Training Courses, for more information visit: > http://www.kitware.com/products/protraining.html > > Please keep messages on-topic and check the ITK FAQ at: > http://www.itk.org/Wiki/ITK_FAQ > > Follow this link to subscribe/unsubscribe: > http://www.itk.org/mailman/listinfo/insight-users > Powered by www.kitware.com Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html Kitware offers ITK Training Courses, for more information visit: http://www.kitware.com/products/protraining.html Please keep messages on-topic and check the ITK FAQ at: http://www.itk.org/Wiki/ITK_FAQ Follow this link to subscribe/unsubscribe: http://www.itk.org/mailman/listinfo/insight-users |
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