Coregistration just uses a rigid-body model. You should use at least a
9 or 12 parameter affine transform in order to model the size
differences between the templates in SPM, and your individual subjects.
In general, if you want to derive coordinates in mm from the voxel
indices (numbered from 1..n, rather than 0..n-1), then simply multiply
the indices by the matrix associated with the image (obtained by the
spm_getspace function).
Best regards,
-John
-----Original Message-----
From: SPM (Statistical Parametric Mapping) [mailto:[log in to unmask]]
On Behalf Of Weiying Dai
Sent: Thursday, May 24, 2007 12:33 AM
To: [log in to unmask]
Subject: [SPM] Help on the MNI coordinates
Dear SPMers:
I have a coordinate [x,y,z] in 3D image 'abc.img'(with
[0 0 0] as orgin in abc.hdr, dimension [101 111 121]),
I want to know it MNI coordinates.
I coregistered 'abc.img' to 'T1.mnc', then I got the
.mat file (let us say, 'abc.mat'). I get
transformation matrix ABC (4*4) from 'abc.mat'. Does
my MNI coordinate suppose to be
ABC * [x-101/2 , y-111/2, z-121/2, 1]' ?
Could you please tell me where is wrong?
Thank you very much!
Weiying
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