[VoxBo] converting voxbo to mni or tal

[Daniel Y Kimberg]

Daniel Drucker wrote:
>  I need talairach coords for a maxima. How do I convert voxbo's "
> geometric cent: 34.1306 7.79429 16.7808" into tal space? I have a
> matlab function that purports to go from MNI to TAL, but I don't know
> how to get into MNI in the first place. I tried subtracting the
> origin, I tried subtracting the absolutecornerposition, nothing gives
> a sensible result.

Something like this: first, figure out the right origin for your
volume.  I always forget the origins, but I discovered that the Van
Essen lab has a handy cheat sheet at this address:

http://brainmap.wustl.edu/help/mapper.html

For example, if your volume is 53x63x46, then your origin is likely
26,37,17.  Note that this web page lists 0-indexed origins, so you
shouldn't have to add or subtract 1 to use with VoxBo data.  Now you
can subtract the origin, to get the MNI coordinate in voxels.  Then
multiply by your voxel sizes to get MNI coordinate in mm.  Finally,
convert from MNI to Talairach.

I believe the geometric center is in voxels, but if it's in mm, adjust
these instructions accordingly.  If this doesn't work, then stop by
and we can figure out what's going on.

dan