On Wed, Feb 20, 2008 at 10:46 PM, Doug Greve <greve@nmr.mgh.harvard.edu> wrote:
On Wed, 20 Feb 2008, Mishkin Derakhshan wrote:
> Hi,
>
> 1. When using mris_convert lh.white lh.white.ascii, what co-oridnate
> system are the xyz co-ordinates reported in? ie. is it the RAS
> co-ordinates of the T1.mgz volume?
These are "surface RAS" or "tkregister RAS". There is a power point
presentation on coord systems on the wiki.
So according to the overview on
https://surfer.nmr.mgh.harvard.edu/fswiki/CoordinateSystems if I
wanted to go from the SurfaceRAS (ie. what the lh.white.ascii is in)
back to the coord system of my original volume, i would transform my
object with the matrix M = inv(xform3)*inv(xform2)*inv(xform1) ?
The diagram leads me to believe this is the same as M = inv(4)*inv(1) ?
The text also says the SurfaceRasFromVoxel matrix is:
[ 3x3 part (t1 - c_r)]
[ same as (t2 - c_a)]
[ xform0 (t3 - c_s)]
[ 0 1 ]
So the inverse of that would be what I'm looking for as well right? In
that case, what is xform0? Just my directional cosines of the original
image? Would t1,t2,t3 =0 then?
thanks for the help,
mishkin
> 2. I am making the assumption that the lh.white and the lh.pial will
> always have the same number of indices and polygons. Can I also make
> the assumption that the order in which they are printed using
> mris_convert will be the same. ie. Will the vertex on line 54 of
> lh.white.ascii correspond to the same vertex on line 54 of
> lh.pial.ascii?
Yes.
doug
> thanks,
> mishkin
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--
Douglas N. Greve, Ph.D.
MGH-NMR Center
greve@nmr.mgh.harvard.edu
Phone Number: 617-724-2358
Fax: 617-726-7422
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