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Dear Elena & SPMers, At 11:00 AM 2/23/2005 +0000, Elena Antonova wrote: >How does one correct for smoothness in ROI? I was simply comparing the >smoothness (number of resels per voxels in the search volume) in the ROI >relative to the average smoothness of the whole image. Is there a >statistical procedure in SPM99 that allows correcting for smoothness in ROI >during SVC? Sorry, i'm not an expert, so would really appreciate your help. First you might want to find the smoothness within your ROI. If you have a binary mask for the ROI, then first you mask the RPV image and calculate the sum of all the RPV voxels in the ROI. This should give you the number of RESELs in your ROI. Then based on the RESELs, you can calculate FWHM as FWHM = V / (RESELs)^(1/3) where V is the number of voxels in the ROI. Once the smoothness is found, then you can change the smoothness for your SVC. In SPM2, this can be done by changing xSPM.FWHM variable with FWHM * [1 1 1] (FWHM in voxels). In SPM99, I think the name of the variable is VOL.FWHM. I haven't used SPM99 for a while... Hope this helps! -Satoru Satoru Hayasaka ============================================== Post-Doctoral Fellow, MR Unit, UCSF / VA Medical Center Email: shayasak_at_itsa_dot_ucsf_dot_edu Phone:(415) 221-4810 x4237 Homepage: http://www.sph.umich.edu/~hayasaka ==============================================================