[Gate-users] Potential bug in ring repeaters in GATE

[Zhengzhi Liu]

Hi Ane,

Thank you very much for taking the time to answer my question. Yes, you
are right. I do need to reset the value of minSectorDifference to 1, which
is default to 2. After resetting the minSectorDifference to 1, everything
works as expected. I used minSectorDifference before, but all of a sudden I
forgot to adjust the value because with the times of ring repeater setting
to 2, these two detector heads are far away from each other and a
minSectorDifference of 2 will make no sense at all. Maybe I
thought minSectorDifference has a default value of 1 (which makes more
sense to me). Anyhow, I will keep it in mind in the future.

Thanks, Ane for the speedy and accurate response.

Best wishes,
Zhengzhi

On Sun, Jan 26, 2020 at 1:17 AM Ane Etxebeste <
ane.etxebeste at creatis.insa-lyon.fr> wrote:

> Hi Zhengzhi,
> By default the minimum sector difference for valid coincidences is set
> to 2.
> If you want to get coincidences with a system composed of two detector
> heads you need to set the minimum sector difference to 1 using the
> following command:
> /gate/digitizer/Coincidences/minSectorDifference 1
> I hope it helps.
> Regards,
> Ane
>
>
> On 2020-01-26 06:13, Zhengzhi Liu wrote:
> > After looking into the singles file, it looks alright. There are many
> > qualified coincidence events in the singles file, but they were not
> > captured by coincidence sorter. This consistently happens when the
> > times of ring repeater is set to 2, but it works fine when the times
> > of ring repeater is set to other values (>2). Thus I believe it might
> > be a bug that set the times of ring repeater to 2 would cause the
> > failure of coincidence sorter in PET.
> >
> > Has anyone experienced this issue before? Any thoughts?
> >
> > Sincerely appreciate any help you can provide.
> >
> > Zhengzhi
> >
> > On Sat, Jan 25, 2020 at 4:12 PM Zhengzhi Liu <zliu36 at stanford.edu>
> > wrote:
> >
> >> It looks like ring repeaters does not like twice, other times of
> >> repartition seem to work fine.
> >>
> >> On Sat, Jan 25, 2020 at 3:53 PM Zhengzhi Liu <zliu36 at stanford.edu>
> >> wrote:
> >>
> >>> Dear GATE developers and users,
> >>>
> >>> I recently came across a weird situation in GATE and have spent a
> >>> few days on it, but still could not figure it out why. Here is the
> >>> problem:
> >>>
> >>> In benchPET [1] and GateContrib [2], the original code works fine,
> >>> but soon as I change the times in the ring repeater to 2 in the
> >>> following code, there will be no coincidence event recorded:
> >>>
> >>> /gate/head/repeaters/insert                          ring
> >>> /gate/head/ring/setRepeatNumber               4
> >>>
> >>> I did check all the details and nothing seems to have been changed
> >>> fundamentally, except that there are fewer detectors in the
> >>> transaxial plane. Even so, there are still two detector panels
> >>> facing each other as shown in the attached figure
> >>> (benchPET_ring_repeaters_2.png). Each detector panel has
> >>> registered many singles as shown in the root plot
> >>> (hits_on_detectors.png). However, there was no coincidence event
> >>> registered, not event a single coincidence event. Originally I
> >>> thought it might be due to low geometrical sensitivity but after
> >>> moving these detector panels closer to each other and increasing
> >>> simulation time, there was still no coincidence event registered.
> >>>
> >>> This phenomenon happens in both PET simulation cases mentioned
> >>> above and other PET simulations. Has anyone come across this
> >>> problem before? Is this a bug or simply my mistake?  Please give
> >>> me any thoughts or help.
> >>>
> >>> Thank you very much,
> >>> Sincere regards.
> >>>
> >>> Zhengzhi
> >
> >
> > Links:
> > ------
> > [1]
> >
> https://github.com/OpenGATE/Gate/blob/develop/benchmarks/benchPET/camera.mac
> > [2]
> >
> https://github.com/OpenGATE/GateContrib/blob/master/imaging/PET/PET_CylindricalPET_System.mac
> > _______________________________________________
> > Gate-users mailing list
> > Gate-users at lists.opengatecollaboration.org
> > http://lists.opengatecollaboration.org/mailman/listinfo/gate-users
>
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