[gate-users] cylindricalPET

[Fernando Rannou]

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
> > > _______________________________________________
> > > gate-users mailing list
> > > gate-users at lphe1pet1.epfl.ch
> > > http://lphe1pet1.epfl.ch/mailman/listinfo/gate-users
> > 
> > _______________________________________________
> > gate-users mailing list
> > gate-users at lphe1pet1.epfl.ch
> > http://lphe1pet1.epfl.ch/mailman/listinfo/gate-users
> > 
> _______________________________________________
> gate-users mailing list
> gate-users at lphe1pet1.epfl.ch
> http://lphe1pet1.epfl.ch/mailman/listinfo/gate-users