Thanks for the explanation, Steve. I'll forward the info to the student.
Cheers,
Martin
Quoting Stephen Smith <[log in to unmask]>:
> Hi - this is just in the bits of code that test for whether the USAN
> (local neighbourhood of similar valued voxels to the centre voxel) is
> empty or not - these constants represent the value which is generated by
>
> the centre voxel itself - which clearly isn't of interest in judging
> whether the USAN is "empty" - hence this value is first subtracted from
>
> the USAN sum. By default, if the USAN is empty, then the algorithm
> reverts
> to the median.
>
> Cheers, Steve.
>
>
> On Mon, 25 Jul 2005, Martin Kavec wrote:
>
> > Hi,
> >
> > I think I address this question mainly to Steve Smith, the author of
> Susan
> > filter.
> >
> > I have a student, who is implementing Susan smoothing filter using ITK
>
> > (www.itk.org) image processing library. In trying to understand FSL
> > implementation he studied susan_smooth.c. However, he can not figure
> out, how
> > were some constants determined:
> >
> > a) 10000 at lines 386, 387 and 390
> > b) 100 at lines 427, 428, 431
> > c) 1000000 at lines 699, 700 and 703
> > d) 20000 at lines 966 and 1156
> > e) 200 at lines 1036 and 1230
> > f) 2000000 at line 1363
> >
> > These constants are always used near-by
> > if ( use_median ), so I assume the logic is similar.
> >
> > I would appreciate your explanation. Thanks in advance.
> >
> > Cheers,
> > Martin
> >
>
> --
> Stephen M. Smith DPhil
> Associate Director, FMRIB and Analysis Research Coordinator
>
> Oxford University Centre for Functional MRI of the Brain
> John Radcliffe Hospital, Headington, Oxford OX3 9DU, UK
> +44 (0) 1865 222726 (fax 222717)
>
> [log in to unmask] http://www.fmrib.ox.ac.uk/~steve
>
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