The smoothing kernel should ideally be 2-3 times the aquisioned voxelsize. So in your case I guess it should be anywhere between 4 and 6.
best,
Nico
-------- Original-Nachricht --------
> Datum: Tue, 23 Nov 2010 04:57:20 -0500
> Von: Victor Terry <[log in to unmask]>
> An: [log in to unmask]
> Betreff: Re: [SPM] FWHM size in SPM software
> Hi Torben,
>
> Thanks. I have checked the image as guided by you. The voxel size is
> 2mm-2mm-2mm which is same as the actual size.
>
> So, the SPM actually consider 4 voxels as the FWHM?
>
> Thanks,
> Tianhao
>
> On Tue, Nov 23, 2010 at 3:59 AM, Torben Ellegaard Lund
> <[log in to unmask]>wrote:
>
> > Dear Victor
> >
> > The FWHM is specified in millimeters. SPM will take your voxelsize into
> > account, if you don't know what your voxelsize is you can determine it
> using
> > Check registration and right click on the image.
> >
> > Best
> > Torben
> >
> >
> > Den 23/11/2010 Uge:47 kl. 02.45 skrev Victor Terry:
> >
> > > Dear SPMers,
> > >
> > > I am using the Gaussian smoothing to preprocess the 3D-MRI images. The
> > FWHM is set as 8mm-8mm-8mm in the interface of the SPM8 software.
> > >
> > > If the size of the voxel in the image is 2mm-2mm-2mm, is the actual
> FWHM
> > 16mm-16mm-16mm?
> > > Does “8mm” in the SPM8 software mean “8 voxels” or not? Is the
> default
> > voxel size 1mm-1mm-1mm or not?
> > >
> > >
> > > Thanks in advance.
> > > Victor
> >
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