[Gate-users] About ASCCI Singles output

[Matthieu MOREAU]

Dear Patay, 

Are you sure that it is the position of the " radioactive decay" (ie the position of the positron in the case of 18F or fastI124 sources when it is a positron wich generate the coincidence), because in the classe "GatePulse.hh", we can read : 

"G4ThreeVector m_sourcePosition; //!< position of the source (NOT the positron) that generated the hit" 

but if it's the "source", it's the positron ? (of course when a "positron coincidence" is generate). 

Thanks if you can help me to understand that... 


--- 
Matthieu MOREAU, PhD student in Nuclear Imaging 
CRCNA - UMR 892 - INSERM (France) // Ecole Nationale Vétérinaire de Nantes ONIRIS - AMaROC - +33 (0) 2 40 68 40 05 

----- Mail original -----

De: "Patay Gergely" <patay.gergely at mediso.hu> 
À: gate-users at lists.opengatecollaboration.org 
Envoyé: Vendredi 7 Décembre 2012 14:36:17 
Objet: Re: [Gate-users] About ASCCI Singles output 

Dear Gaters, 

in the ascii output, the columns described as 'XYZ position of the annihilation' 
do *not* contain the annihilation coordinates, instead, they are 
the XYZ position of the *radioactive decay* which produced the 
soon-to-be-annihilated positron (or, in the case of back-to-back source, the 
origin of the gamma pair). 

This is a rather misleading error in the documentation which survives in the new 
revisions (at least from v3.1 to v6.2, maybe earlier too). The correct label 
should be 'XYZ position of the source' or something like this. 

If you really want to access the actual annihilation coordinates, you either 
have to modify the corresponding source code of Gate, or jump directly into the 
raw Geant4 track dump (enabled by /tracking/verbose 2 ). 

cheers, 
Gergely 

----- 
Gergely PATAY 
Mediso Ltd. 



On 2012-12-07 13:37, Marc Chamberland wrote: 
> Some answers: 
> 
> 1) This is the position of the positron-electron annihilation, not the position 
> of the interaction within the crystal. It makes sense that it occurs very near 
> your source. 
> 
> 2) I don't know. Singles are what you get after the digitizer processes your 
> hits. They should be in your crystal. 
> 
> 3) I don't know. 
> 
> 4) The volume IDs are exactly what the name says: the ID (identification 
> number) of the volume in which the hit (or single) occurred. Each volume in 
> each level of the hierarchy of the system you're using (e.g. base, rsector, 
> module, etc.) gets a unique ID number. The volumes get numbered sequentially. If 
> you use a cubic array repeater, then the volumes are numbered 0 to N-1 (where N 
> is the number of volumes you have in your array) and they increase first along 
> the x axis, then along y, then along z. For a ring repeater, they increase in 
> the counterclockwise direction, if I remember correctly. 
> 
> Hope this helps! 
> Marc 
> 
> 
> 
> __________________________ 
> 
> Marc Chamberland, MSc 
> PhD candidate 
> Department of Physics 
> Carleton University 
> Ottawa (ON) 
> 
> 
> On 2012-12-07, at 5:33 AM, open researcher <openresearcher90 at gmail.com 
> <mailto:openresearcher90 at gmail.com>> 
> wrote: 
> 
>> I want some clarifications regarding the output of Singles output - 
>> 1. What does XYZ position of the annihilation in world referential mean. (I 
>> have defined a source at 0, -22, 0 cms (and y axis is depth axis) and a NaI 
>> crystal at -15 cm. Singles file has readings like 0.000e+00 -2.200e+02 
>> 0.000e+00 since the interaction is happening in the crystal I think the 
>> y-coordinate must be -15 cm I don't know how it is showing the coordinate of 
>> the source) 
>> 2. XYZ position of the single in the world referential shows (0, 1, 0) for 
>> some singles, (0, 2, 0) for some and (0, 0, 0) for some singles. what can I 
>> infer from this ? 
>> 3. for some Singles time stamp is -ve (what can it mean ?) 
>> 4. what are Volume IDs ? 
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> 
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