The smoothing works through iterative nearest neighbor smoothing, so the fwhm is essentially discretized because you can't have fractions of an iteration. It looks like fwhm=0.66 is closer to 0 iterations than 1 iteration, so it chooses 0.
On 12/21/18 11:23 AM, shahin@nmr.mgh.harvard.edu wrote:
Dear Surfers, I am trying to use mris_fwhm to apply fwhm=0.66 to my fmri data (voxel size 1 mm iso)using the below command:
mris_fwhm --s <SBJ_NAME>--hemi rh --smooth-only --i fmcpr.sm0.self.projfrac_0.rh.nii.gz --fwhm 0.66 --o fmcpr.sm0p66_surf.self.projfrac_0.rh.nii.gz --mask /masks/brain.self.rh.nii.gz
When I apply this command, it works without any error. The message on screen is as below:
<SBJ_NAME> rh white Number of vertices 160391 Number of faces 320778 Total area 102725.085938 GroupSurface 0 AvgVtxArea 0.640467 AvgVtxDist 0.875515 StdVtxDist 0.253406 Loading mask masks/brain.self.rh.nii.gz Found 36045 voxels in mask Not Polynomial detrending Smoothing input by fwhm=0.660000, gstd=0.280276, niters=0 Only smoothing, so saving and exiting now
But the outcome is the same as input. I think it is expected based on(niters=0). When I use the same command with fwhm =1, then i see the difference and niters=1.
My question is, why is fwhm = 0.66 not acceptable? How can i solve this issue.
Regards
Shahin Nasr
Assistant Prof. in Radiology Harvard Medical School Martinos Imaging Center, MGH Bldg 149, 13th street, Charlestown, MA 02129
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