Hi all, Recently I have been trying to reconstruct a mrs voxel using mri_volsynth using the VOIpositions given in the .rda file. The VOI co-ordinates are as follows: VOIPositionSag 31.6911 VOIPositionCor -25.1448 VOIPositionTra 24.5879
When I input these co-ordinates into mri_volsynth the voxel is in the wrong location. However when I reverse the sign for the Sag and Cor positions then the voxel is very close to right position. After a lot of trial and error I found that after inverting the sign for the X and Y co-ordinates, I have to then +1 on all 3 positions in order for the synthesised volume to be in the correct position.
So using the three positions shown above I have to use the following command:
mri_volsynth --dim 18 18 18 1 --pdf const --c_ras -30.6911 26.1448 25.5879 --o filename
Can anyone explain why I have to reverse the sign and add 1 in order for the voxel to be in the correct location? Is it something to do with using the dcm2nii converter? Also is it normal for the .rda to give the co-ordinates for the centre of the voxel rather than the top corner of the voxel?
Thanks Todd