Thank you for your answer. Just one more question, is the "fsaverage"
already in MNI305 space? In this case, the RAS coordinates from
tksurfer/QDEC are already MNI?
Regards,
Yolanda
2012/6/7 Douglas N Greve <gr...@nmr.mgh.harvard.edu>
> Here are instructions to go from a surface RAS to the mni305 RAS, so
> just invert them.
> doug
>
>
> I have an RAS point on the surface (tkrR tkrA tkrS) ("Vertex RAS" from
> tksurfer) and want to compute the MNI305 RAS that corresponds to this
> point:
>
> MNI305RAS = TalXFM*Norig*inv(Torig)*[tkrR tkrA tkrS 1]'
> TalXFM: subject/orig/transforms/talairach.xfm
> Norig: mri_info --vox2ras orig.mgz
> Torig: mri_info --vox2ras-tkr orig.mgz
>
> Test: click on a point in tksurfer. Use "Vertex RAS" to compute
> MNI305RAS. Compare MNI305RAS to "Vertex MNI Talairach". Also, hit Save
> Point in tksurfer. In tkmedit, Goto Saved Point, compare MNI305RAS to
> "MNI Coordinates". Note: you may need to use the "Volume RAS" from
> tkmedit in the computation above to get an exact match.
>
>
>
> On 06/06/2012 09:43 AM, Yolanda Vives wrote:
> > Dear Freesurfer experts,
> >
> > How can I transform from MNI coordinates to RAS surface coordinates?
> >
> > Regards,
> > Yolanda
> >
> >
> > 2012/6/5 Yolanda Vives <yvi...@pic.es <mailto:yvi...@pic.es>>
> >
> > Dear Freesurfer experts,
> >
> > I have performed a VBM analysis with SPM, using some VOIs. Now I
> > would like to compare the volumetric results obtained with SPM
> > with those of cortical thickness obtained with Freesurfer in the
> > same VOIs (approximately).
> >
> > For this purpose, I would like to transform the MNI coordinates of
> > my SPM VOIs into RAS surface coordinates of fsaverage, to draw a
> > label of more or less the same size of the SPM VOI and to propage
> > it to all the subjects in order to obtain an average cortical
> > thickness of this label (VOI) for each subject.
> >
> > 1) Would this procedure be correct?
> >
> > 2) How could I transform my MNI coordinates into RAS surface
> > coordinates?
> >
> > Thank you in advance,
> > Yolanda
> >
> >
> >
> >
> > --
> > Yolanda Vives
> > PIC (Port d'Informació Científica)
> > Campus UAB, Edificio D
> > E-08193 Bellaterra, Barcelona
> > Telf. +34 93 586 8232
> > http://www.pic.es
> > Avis - Aviso - Legal Notice: http://www.ifae.es/legal.html
> >
> >
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> > Freesurfer@nmr.mgh.harvard.edu
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>
> --
> Douglas N. Greve, Ph.D.
> MGH-NMR Center
> gr...@nmr.mgh.harvard.edu
> Phone Number: 617-724-2358
> Fax: 617-726-7422
>
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>
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--
Yolanda Vives
PIC (Port d'Informació Científica)
Campus UAB, Edificio D
E-08193 Bellaterra, Barcelona
Telf. +34 93 586 8232
http://www.pic.es
Avis - Aviso - Legal Notice: http://www.ifae.es/legal.html
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