Dear all,

     I am trying to estimate smoothness for each subject with the following steps (https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=ind1505&L=spm&D=0&P=558407), however, output values are too high.

     1. calculate the square root of the ResMs.img:

                           spm_imcalc_ui([pwd,'\ResMS.img'],[pwd,'\sqrt_ResMS.img'],'sqrt(i1)');

     2. estimate smoothness:

            FWHM=spm_est_smoothness([pwd,'\sqrt_ResMS.img'],[pwd,'\mask.img'],[624,1]); % two runs, 312 scans in each, this makes n=624

                                                                                                            %mask.img was generated at the first-level analysis for a given subject

     The output of these steps are pretty high (as compared to the values in SPM.xVol.FWHM = 4.5, 4.5, 4.4):

In addition, according to a previous thread (https://www.jiscmail.ac.uk/cgi-bin/webadmin?A2=ind1506&L=spm&P=R1499&1=spm&9=A&J=on&d=No+Match%3BMatch%3BMatches&z=4), using ResMS.img will result in larger FWHM estimates, however, this seems not the case here:

using: FWHM=spm_est_smoothness([pwd,'\ResMS.img'],[pwd,'\mask.img'],[624,1]).

Did I use spm_imcalc_ui or spm_est_smoothness in a wrong way? Any comments will be appreciated!