Dear SPMers;

I need to find the corresponding voxel in a functional image for a specific structural image voxel after coregistering two images. My structural image has 256*256*125 voxels and the functional image has 64*64*30 voxels. 

Previously Dr. Ashburner replied to a similar question like this  as follows:

Mapping from voxel i,j,k in image A.img to the appropriate voxel in image B.img would be done by:

   MA=spm_get_space('A.img');

   MB=spm_get_space('B.img');

   M = MB\MA;

   vox = M(1:3,:)*[i; j; k; 1]

Note that voxels are indexde from 1..N rather than from 0..N-1.

However;  as an example when I try to map voxel (169 , 62 ,35) of the anatomical image to the functional space using the above formula; I get 

-193.7016 

  675.7443

  481.0961

 (I couldnot attach the structural and functional image because of quota limitation)

as the corresponding voxels'  coordinates at the functional space which is far beyond the functional volume size. 

In one of the SPM course slides; I have read that 

Registering image B (source) to image A (target) will update B’s voxel-to-world mapping

*  Mapping from voxels in A to voxels in B is by *  A-to-world using MA, then world-to-B using MB-1 : MB-1 MA

I also tried to implement this but still cannot manage to use the trasfer matrices appropriately. 

Your help will be greatly appreciated. 

Thank you;

Sinem Burcu ERDOGAN