[gate-users] cylindricalPET

[Yun Dong]

Hi Fernando,
Thanks for your help. I have tried that the gamma ray go straight into 
panels, and I also increase the activity to 100M Bq, but the result 
seem be same till now. I am afraid that the problem would not be from 
my setting but the GATE. Thanks.

Yun

----- Original Message -----
From: Fernando Rannou <rannou at diinf.usach.cl>
Date: Monday, July 18, 2005 12:23 pm
Subject: Re: [gate-users] cylindricalPET

> Hi Yun,
> you could try to "focus" the backtobacks
> into the panels, that is modify
> 
> /gate/source/twogamma/gps/mintheta 0.deg 
> /gate/source/twogamma/gps/maxtheta 180.deg
> /gate/source/twogamma/gps/minphi 0. deg
> /gate/source/twogamma/gps/maxphi 360. deg
> 
> such that they always go in the direction of the detectors.
> I have the feeling that you just have a sensitivity problem,
> in the sense that the solid angle of your scanner is so small that 
you
> need a lot, lot of events to get some coincidences. That would
> explain why you get some coincidences when you have more panels.
> So try to shoot the gammas straight into the detectors.
> 
> 
> Fernando
> 
> 
> On Mon, 2005-07-18 at 16:23 -0500, Yun Dong wrote:
> > Hi Fernando,
> > 
> > Thanks for your reply. I give my some configures of simulation 
here:
> > 
> > Geometry: ~250mm*175mm dual-panel, distance between them is 50mm
> > # P H Y S I C S
> > /gate/physics/gamma/selectCompton standard
> > /gate/physics/gamma/selectPhotoelectric standard
> > /gate/physics/gamma/selectRayleigh lowenergy
> > /gate/physics/setElectronCut 300. cm
> > /gate/physics/setXRayCut 1. GeV
> > /gate/physics/setDeltaRayCut 1. GeV
> > # D I G I T I Z E R
> > /gate/digitizer/Singles/insert adder
> > /gate/digitizer/Singles/insert readout
> > /gate/digitizer/Singles/readout/setDepth 1
> > /gate/digitizer/Singles/insert blurring
> > /gate/digitizer/Singles/blurring/setResolution 0.15
> > /gate/digitizer/Singles/blurring/setEnergyOfReference 511. keV
> > /gate/digitizer/Singles/insert thresholder
> > /gate/digitizer/Singles/thresholder/setThreshold 250. keV
> > /gate/digitizer/Singles/insert upholder
> > /gate/digitizer/Singles/upholder/setUphold 750. keV
> > /gate/digitizer/Coincidences/setWindow 100. ns
> > # S O U R C E S
> > /gate/source/addSource twogamma
> > /gate/source/twogamma/setActivity 1000000. becquerel
> > /gate/source/twogamma/setType backtoback
> > /gate/source/twogamma/gps/particle gamma
> > /gate/source/twogamma/gps/energytype Mono
> > /gate/source/twogamma/gps/monoenergy 0.511 MeV
> > /gate/source/twogamma/gps/centre 0 0 0 mm
> > /gate/source/twogamma/gps/type Volume
> > /gate/source/twogamma/gps/shape Sphere
> > /gate/source/twogamma/gps/radius 0.5 mm
> > /gate/source/twogamma/gps/confine NULL
> > /gate/source/twogamma/gps/angtype iso
> > /gate/source/twogamma/gps/mintheta 0. deg
> > /gate/source/twogamma/gps/maxtheta 180. deg
> > /gate/source/twogamma/gps/minphi 0. deg
> > /gate/source/twogamma/gps/maxphi 360. deg
> > 
> > Just now I made some tests with resetting configure in 
> "benchmarkPET"> coming with GATE package: 
> > 1. (camera.mac 127L) /gate/head/ring/setRepeatNumber 4 (I also 
> try 2)
> > 2. (benchmarkPET.mac 
> 45L)/gate/output/ascii/setOutFileCoincidencesFlag 1
> > (enable ascii coincindences output).
> > Then I find that when two heads, the size of coincindence ascii 
> output> file is always zero after simulation start. But when 4 
> heads, the size
> > increases during the simulation. That's so confusing. 
> > 
> > Thank you again.
> > 
> > Best Regards
> > Yun
> > 
> > 
> > 
> > ----- Original Message -----
> > From: Fernando Rannou <rannou at diinf.usach.cl>
> > Date: Monday, July 18, 2005 11:28 am
> > Subject: Re: [gate-users] cylindricalPET
> > 
> > > Hi Yun
> > > you should get coincidences. Among the questions I would ask are:
> > > 1) What kind of output are you using? I assume you set the 
> digitizer> > appropriately to collect coincidences.
> > > 2) how much activity, for how long?
> > > 3) are you simulating a positron emitter (of course)?
> > > 4) How big are the detectors with respect to the FOV?
> > > 
> > > Fernando
> > > 
> > > 
> > > 
> > > On Mon, 2005-07-18 at 12:10 -0500, Yun Dong wrote:
> > > > Hi everyone,
> > > > I am just simulating two parallel-panels PET system through
> > > > cylindricalPET system in GATE. Howver, I never get 
> coincidences, 
> > > just> GateSingles. Does it mean that cylindricalPET can never 
> > > simulate the
> > > > open two parallel-detector PET system? Dose anybody have 
> some idesa?
> > > > Thank you so much.
> > > > 
> > > > Best Regards
> > > > Yun
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