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

[Andrew Janke]

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
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