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They go into the "sform" matrix of the NIfTI header (and sometimes also into the "qform" fields). The particular fields are:

 float srow_x[4] ;    /*!< 1st row affine transform.   */
 float srow_y[4] ;    /*!< 2nd row affine transform.   */

 float srow_z[4] ;    /*!< 3rd row affine transform.   *

These are described at http://nifti.nimh.nih.gov/pub/dist/src/niftilib/nifti1.h , with a bit more general information at http://nifti.nimh.nih.gov/nifti-1 .

If you want to read the fields in SPM, then the values can be obtained by:

P=spm_select(1,'nifti');
Nii = nifti(P);
disp(Nii.mat);

Note also that there's a hidden Nii.hdr field in the NIfTI structure, which shows the values actually saved in the header. Values shown for Nii.mat assume that voxels are indexed by 1..N (as in MATLAB), whereas values in the Nii.hdr.srow_x/y/z assume that voxels are indexed by 0..N-1.

Best regards,
-John

On 18 January 2011 16:16, giuliana faiella <[log in to unmask]> wrote:

Dear all,

I have a question for you:

In the coreg_estimate the registration parameters are stored in the headers of the source. Does somebody know where exactly?

Thank you a lot in advance!

Giuliana