--- Ged Ridgway <[log in to unmask]> wrote:
> Hi Joe,
>
> > I have two data sets which I can use SPM to
> register one to the other.
> > Here comes the question: can I possibly convert
> (register) say a voxel
> > of coordinate (x,y,z) at floating volume to
> (x',y',z') on the space of the
> > reference space?
>
> You can. How easily depends on how you registered
> them. If they are
> just rigidly or affinely registered (e.g. with
> realign, or coreg,)
> then the matrices in the vol.mat fields (after
> mapping the images with
> spm_vol) relate the coordinate systems quite simply.
>
> E.g. something like:
> xyz1 = [x y z 1]'; % -- voxel (homogeneous)
> coords, image 1
> XYZ1 = vol1.mat*[xyz1 1];
> % -- world coords (in both *registered* images)
> xyz2 = vol2.mat\XYZ1; % voxel coords, image 2
>
> If you've used non-linear normalisation, or SPM5's
> unified
> segmentation and normalisation, then the easiest way
> appears to be to
> convert the sn.mat (or inv_sn.mat, check the first
> post below
> carefully to be sure which you want) into a
> deformation field, and
> then read the voxels from this, see the following:
>
>
http://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=ind0702&L=SPM&P=R47018
>
> and the parts of this which are relevant for reading
> from the
> deformation field, after you have read the above,
>
>
http://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=ind0702&L=SPM&P=36372
>
> Best,
> Ged.
>
Hi, Ged,
Thanks a lot for your help.
The first solution in rigid/affine transformation:
say, I've got a sn.mat from coreg. Then I should apply
the following: [x y z 1] / Affine. Where Afffine is
the affine transformation parameter matrix. Am I
right?
In case of normalisation, from the two links you gave
me:
with sn.mat from normalisation, all I can do to look
at a few voxels in the registered image for
coordinates reading ( manual ). Is it right?
Thank you so much,
Joe
__________________________________________________
Do You Yahoo!?
Tired of spam? Yahoo! Mail has the best spam protection around
http://mail.yahoo.com
|