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

[Ane Etxebeste]

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
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