[Gate-users] No data output when using optical processes (GATE V5.0.0_p01)

[Uwe Pietrzyk]

Hi Melanie,

let me try to answer at least some of your questions. In case
I don't know, I will make sure that you get an answer soon.

On 05.11.2009, at 13:57, Melanie Hohberg wrote:

Hi Uwe,

thank you very much for offering me some help with Gate.
Actually I have a bunch of questions:

In the example code there are defined two chains, one for the traditional Singles and one for the optical photons (OpticalSingles).
The readout is defined as the following:
/gate/digitizer/Singles/readout/setDepth 3
Is it also necessary to define this for the OpticalSingles?
No, as far as I know, it is not required. Did you try and did it work?
Optical Singles just handle the energy in a different way (see below)
/gate/digitizer/OpticalSingles/readout/setDepth 3

What should be specified as sensitive detector (attachCrytalSD)?
The scintillation crystal or the photosensor (PMT,APD,...) or both?
Anything you want to have treated as an attenuating or scattering media
should be declared as SD = sensitive detector. But there is just one
object attached to the system as the final detector, where the coordinates
are stored from, like GlobalX, ...
How is the energy spectrum from the Singles determined?
Is it calculated from the number of detected optical photons or is it determined from a previous defined energy and time resolution in the macro?
I do not know precisely the algorithm, but since the energy of a gamma, say 511 KeV,
which is stopped in a LSO crystal, converts into a number of optical photons in the crystal
according to a statistical process, it should work in exactly this way. The data file
Materials.xml contains the number of Photons created by a 1 MeV gamma in LSO,
which is 26000. You can look into the enery-leave of the OpticalSingles branch
and this distribution should have the x-axis tending to max of about 12000 to 13000, since
we are dealing with a statistical process.


Is it possible to extract information about the number of reflections that occured for one photon before getting detected?
Actually, this should be possible by studying the entries in the hits-branch. I haven't got that far and also
none of my colleagues at Juelich. So I will ask the experts tomorrow, since we have a
GATE-Collaboration-Meeting in Orsay near Paris.

Hope this helps.

Kind regards from Paris,

Uwe

Best regards,
Melanie


Melanie Hohberg

Klinikum rechts der Isar der Technischen Universität München
Nuklearmedizinische Klinik und Poliklinik
Ismaninger Str. 22
81675 München
Tel: 0049 (0)89 4140 6457
Fax: 0049 (0)89 4140 4938
Email: melanie.hohberg at tum.de<mailto:melanie.hohberg at tum.de>
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Prof. Dr. Uwe Pietrzyk
Diplom-Physiker
Institut für Neurowissenschaften und Medizin / INM-1
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