Hi Daniel,
Many thanks for the suggestions. I'm still a bit confused by how to approach this problem. The SSS ROI I was provided with occurs in a different space than the native space for my subject. It is not an ROI from an atlas. It fits on the right area of the template image they provided me with. But how do I transform that ROI so it fits on the right area of each subject's anatomical? The 3dNwarpApply command seems to require a specific transformation file for the -nwarp option. How do I create this file, which is needed to correctly specify the transformation that needs to be applied?
Alain