[Gate-users] Estimate randoms from ROOT-file

[Simon Stute]

Hi,

2010/3/11 Ida Häggström <ida.haggstrom at radfys.umu.se>

> Hi Claude!
> Thank you for your reply! I've briefly started looking at the delayed
> window
> but have not gotten so far yet. I've looked in the users guide but not been
> able to figure it all out yet... Using ROOT output, do you know if the
> delayed coincidence branch can be rebinned into sinograms just like the
> ordinary coincidence data (and then subtracted from the ordinary
> sinograms)?
> Or is this correction implemented directly by GATE, i.e. GATE subtracts the
> randoms from the prompts directly?
>


The delayed coincidence sorter will create another tree in the root file.
So you rebin your delayed coincidences into a delayed sinogram.
And latter you subtract this sinogram to your prompt sinogram (it depends on
which reconstruction scheme you use).
The correction is of course not performed online to give better flexibility
in data processing.

Cheers,
Simon



>
> Thanks!
> Ida
>
> Den 11 mars 2010 10.36 skrev COMTAT Claude <claude.comtat at cea.fr>:
>
> > Hi Ida,
> >
> > Rather than estimating the random coincidences from the singles, you can
> > simulate a delayed coincidence window within Gate in addition to the
> prompt
> > coincidences, and use it to correct for random coincidences.  To add a
> > delayed coincidence window, see the users guide:
> >
> > "By default, the offset value is equal to 0, which corresponds to a
> prompt
> >    coincidence sorter. If a delayed coincidence sorter, with 100 ns time
> > shift, is to be simulated, one should specify the offset value with the
> > command:
> > /gate/digitizer/Coincidences/setOffset 100. ns"
> >
> > Claude
> >
> > -----Message d'origine-----
> > De : gate-users-bounces at lists.opengatecollaboration.org [mailto:
> > gate-users-bounces at lists.opengatecollaboration.org] De la part de Ida
> > Häggström
> > Envoyé : jeudi 11 mars 2010 09:39
> > À :
> > Objet : [Gate-users] Estimate randoms from ROOT-file
> >
> > Hello!
> >
> > I'm trying to create a randoms sinogram (not the "true randoms", but an
> > estimate) to use for randoms correction for later reconstruction in STIR.
> >  I
> > guess the most common way is to use the singles countrates for each LOR
> > (?).
> > I am not familiar with ROOT so I'm having some problems... Has anyone
> > managed to estimate the randoms from the ROOT output files? I would
> really
> > appreciate any help!
> >
> > Thanks!
> > Ida
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