[Gate-users] Estimate randoms from ROOT-file

[Ida Häggström]

Thank you Claude and Simon for your tips! I will look into the delayed
window and go from there..
Thanks again!
Ida

Den 11 mars 2010 11.54 skrev Simon Stute <gate.stute at gmail.com>:

> 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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