[gate-users] Very low number of scatter in GE Discovery

[Fernando Rannou]

Hi
How do you count the scatter events? In Root?

Fernando

On Tue, 2006-03-07 at 10:59 -0500, Mikhail Shilov wrote:
> Dear Gate group,
> 
> I was investigating the fraction of scatter in GE discovery in normal
> and in 3D mode ( no septa).
> I ran a simple simulation (see the attached file) with 3 cylindrical
> F-18 sources inside a 20 cm radius and 30 cm height cylindrical phantom
> and recorded gateSingles.dat and gateCoincidences.dat files. I then
> looked at the number of recorded coincidences with at least one Compton
> scatter inside the phantom. It turned out that this number is ~0.5%
> (~0.8% in 3D) of total recorded coincidences.
> This is not what I would expect from the literature ( ~30%). The
> fraction of singles is what I expected ~ 30%
> 
> I was wondering if anyone looked as this issue before and if my result
> is reasonable.
> 
> Here is my digitizer script:
> 
> #       A D D E R
> /gate/digitizer/Singles/insert adder
> #       R E A D O U T 
> /gate/digitizer/Singles/insert readout
> /gate/digitizer/Singles/readout/setDepth 1
> #      E N E R G Y   B L U R R I N G
> /gate/digitizer/Singles/insert blurring
> /gate/digitizer/Singles/blurring/setResolution 0.15
> /gate/digitizer/Singles/blurring/setEnergyOfReference 511. keV
> #       E N E R G Y   C U T
> /gate/digitizer/Singles/insert thresholder
> /gate/digitizer/Singles/thresholder/setThreshold 300. keV
> /gate/digitizer/Singles/insert upholder
> /gate/digitizer/Singles/upholder/setUphold 650. keV
> #       D E A D    T I M E 
> /gate/digitizer/Singles/insert deadtime
> /gate/digitizer/Singles/deadtime/disable
> /gate/digitizer/Singles/deadtime/setMode nonparalysable
> /gate/digitizer/Singles/deadtime/chooseDTVolume block
> #       C O I N C     S O R T E R 
> /gate/digitizer/Coincidences/setWindow 12.5 ns
>   
> 
> Mikhail A. Shilov
> The Johns Hopkins University
> Department of Radiology
> Division of Medical Imaging Physics
> Tel:   (410)502-3773
> Fax:  410-614-1977
> mailto: mshilov1 at jhmi.edu
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