[MINC-users] voxel coordinates in native space vs.

[jarv0075]

One easy way is to open the transform file, add the 0,0,0,1, invert it,
then use mincresample -like 'native.mnc' with the new transform..

If you do it manually, you have to apply the inverse transform, then apply
a transform to account for non-isotropic voxels, then translate it back to
its original position in the volume via the mincinfo xstart ystart zstart.


On 21 May 2004, Andrew Janke wrote:
> On Tue, 18 May 2004, Jeni Chen wrote:
> 
> > I'm just wondering if anyone knew how to convert a set of tal
coordinates
> > back into native space (i.e finding the equivalent). For instance, take
> > the Talairach coordinates 6 -8 44. In register we see the corresponding
> > voxel coordinates as 48 59 58. But if I want to look for the exact same
> > peak in the original raw data, how can I find it? Is there a
> > program or mathematical formula to do it?
> 
> Jeni,
> 
> All you need do is find the .xfm file that was generated to register your
> file
> to talairach space (assuming you used mritotal to do this).
> 
> Have a look at this file, it contains a truncated 4x4 affine
transformation
> matrix (assuming you did a linear fit only), the last row (0 0 0 1) is
not
> stored.
> 
> Then just take your point in talairach space, transform this by the
inverse
> of
> the Matrix in the .xfm file and you have your point in native space.
MATLAB
> or
> octave may prove handy to do this matrix calculation.
> 
> 
> --
> Andrew Janke  ( rotorATcmr.uq.edu.au || www.cmr.uq.edu.au/~rotor )
> Australia->University of Queensland->Centre for Magnetic Resonance
> W: +61 7 3232 7254  ||  H: +61 7 3800 4042  ||  M: +61 4 2138 8581
> _______________________________________________
> MINC-users@bic.mni.mcgill.ca
> http://www.bic.mni.mcgill.ca/mailman/listinfo/minc-users
> 

-------------------------------------
Timothy R. Jarvis
email: tjarvis@cs.umn.edu
cell:  612-554-4641
-------------------------------------