[Gate-users] a question about CT source

Devin VanElburg vanelbud at tbh.net
Thu Aug 20 18:31:48 CEST 2015

Hello Masoud,

I may be wrong, but this is how I believe it works. Each point you define is the energy value in MeV, then the height of that point. So you need to define your spectrum, say for an energy distribution from 0-1MeV for example:

/gate/source/xraygun/gps/histpoint 0.1 0.005
/gate/source/xraygun/gps/histpoint 0.2 0.01
/gate/source/xraygun/gps/histpoint 0.3 0.03
/gate/source/xraygun/gps/histpoint 0.4 0.7
/gate/source/xraygun/gps/histpoint 0.5 1.0
/gate/source/xraygun/gps/histpoint 0.6 1.0
/gate/source/xraygun/gps/histpoint 0.7 0.7
/gate/source/xraygun/gps/histpoint 0.8 0.03
/gate/source/xraygun/gps/histpoint 0.9 0.01
/gate/source/xraygun/gps/histpoint 1.0 0.005

>From what I see in the forums, people have given the second value either as a normalized value (like I have done with the peak at 1.0), or as actual data (in this case, I suppose the distribution would be automatically normalized?).

I'm going off the forums from here:

Can someone confirm what I've explained, or correct me if I'm way wrong?

Devin Van Elburg
Physics w/ c/ Biomedical Physics
Lakehead University
>>> Masoud  08/20/15 11:57 AM >>>
Dear all,

I am trying to simulate a CT scanner. For source definition, I need to use arbitrary point-wise spectrum "Arb" as following command:

/gate/source/xraygun/gps/histpoint energy (MeV)     ????

Please guide me what is the second column in the command? Photon fluence (photon/mm2.s)? or photon flux (photon/s)? or number of photons in source?

Best Regards,


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