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You need to enter smoothness in millimeters, not voxels. The value in SPM.xVol.FWHM is in voxel units, so you either need to multiply it by your voxel sizes, or you can find the values in mm on the bottom of the results table within SPM. Not sure how directly AFNI's estimates will compare to that (just at a glance it seems AFNI is producing smaller estimates if you're using the default 2mm voxel size in SPM). -Mike -- Mike Angstadt Research Computer Specialist / PANLab Lab Manager Department of Psychiatry / University of Michigan (734) 936-8229 > -----Original Message----- > From: SPM (Statistical Parametric Mapping) [mailto:[log in to unmask]] > On Behalf Of Neuroimage Analyst > Sent: Tuesday, July 26, 2016 6:41 PM > To: [log in to unmask] > Subject: [SPM] FWHM: SPM and AFNI > > Hi, > > I processed my images using SPM and obtained a statistical T-map. > > I want to use 3dClustSim in AFNI to correct for FWE. > > In order to get FWHM to put as an input to 3dClustSim, there are 2 > alternatives: > 1) Using SPM.mat > SPM.xVol.FWHM gives me 5.8062 6.3335 6.4607 > > 2) Using AFNI > 3dcalc -a ResMS.hdr -expr "sqrt(a)" -prefix sqrt_Res_MS.nii 3dFWHMx -mask > MNI_2mm.nii -input sqrt_Res_MS.nii - output fwhm.txt gives me: 9.36413 > 9.74247 8.29123 > > Which one should I pass in 3dClustSim? > > Thanks > > Regards ********************************************************** Electronic Mail is not secure, may not be read every day, and should not be used for urgent or sensitive issues