[MINC-users] CIVET-1.1.12 and sqrt(2) offset

[Gabriel A. Devenyi]

Thanks so much!

Perhaps this info would make a helpful note on the CIVET-1.1.12
documentation page?

-- 
Gabriel A. Devenyi B.Eng. Ph.D.
Research Computing Associate
Computational Brain Anatomy Laboratory
Cerebral Imaging Center
Douglas Mental Health University Institute
McGill University
t: 514.761.6131x4781
e: gdevenyi at gmail.com

On Tue, Jan 6, 2015 at 10:39 AM, Claude LEPAGE <claude at bic.mni.mcgill.ca>
wrote:

> Hi,
>
> You have to multiply by sqrt(2) to obtain the correct fwhm in
> CIVET-1.1.12 for surface blurring.
>
> -thickness tlink fwhm_desired*sqrt(2)
> -area-fwhm fwhm_desired*sqrt(2)
> -volume-fwhm fwhm_desired*sqrt(2)
>
> For example, if you want fwhm=20mm, you have to specify
> 20*sqrt(2)=28.28. However, since fwhm is used in the
> filename for the thickness files, I suggest to round
> fwhm if you don't want filenames with a dot in them.
>
> If you used a value of 30mm before, then this corresponds
> to an effective fwhm of 30/sqrt(2)=21.21mm.
>
> Sorry for the inconvenience.
>
> Claude
>
>
> >
> > Hi all,
> >
> > I was previously aware that CIVET-1.1.12 has a sqrt(2) mistake according
> to
> > the CIVET-2.0 changelog: "corrected fwhm for surface smoothing (was off
> by
> > sqrt(2) in 1.1.12)"
> >
> > Is the "fwhw for surface smoothing" one of the command-line parameters
> that
> > could be adjusted to compensate? (my only guess is is "-area-fwhm
> <fwhm>")
> > If so, is it bigger or smaller by sqrt(2)?
> >
> > Thanks!
> >
> > --
> > Gabriel A. Devenyi B.Eng. Ph.D.
> > Research Computing Associate
> > Computational Brain Anatomy Laboratory
> > Cerebral Imaging Center
> > Douglas Mental Health University Institute
> > McGill University
> > t: 514.761.6131x4781
> > e: gdevenyi at gmail.com
> > _______________________________________________
> > MINC-users at bic.mni.mcgill.ca
> > http://www.bic.mni.mcgill.ca/mailman/listinfo/minc-users
> >
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