Dear SPMers, I have used SPM realign to perform a realignment of a later image to an earlier image. I would now like to perform an inverse realignment of a tracing performed on the earlier image (and converted to analyze format) into the space of the later image. I was wondering how to manipulate the .mat file to get the inverse realignment? I realize that I could just run realign again in the opposite direction, transfer the .mat data to the traced image using spm_vol and spm_write_vol, then perform spm_reslice, but figured there might be a less computationally intensive/time-saving way to calculate the .mat data than running spm_realign again in reverse. Thanks for any help you may have to offer. Lynne