Can we simulate megavoltage photon beams with MC-GPU?

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I'm wondering if I can run your code to simulate high energy interaction 
between photons and objects? 
For treatment purpose, 6 and 18 MV x-rays are commonly used. According to your 
published paper, the code can simulate photons with energy up to 1 GeV. 

Does this mean I can use it to simulate the high-energy treatment beams (6 and 
18 MV)?

Original issue reported on code.google.com by diamc...@gmail.com on 9 May 2011 at 7:12

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The photon transport physics functions in MC-GPU are essentially a translation 
of the PENELOPE 2006 subroutines for sampling Compton and Rayleigh scattering.
The only difference in the code is that PENELOPE does not simulate Doppler 
broadening for energies above 5 MeV (penelope.f line 5872) while MC-GPU does 
(all photons are simulated equally for maximum parallelization capability). 
I have not checked if this modification changes in any way the simulation but I 
don't expect so because at high photon energies the Doppler broadening should 
be negligible (the energy of the photon is much larger than the energy of the 
target electron).

You can use the code for high energy photons but make sure that pair production 
and bremsstrahlung of secondary electrons are not relevant in your application. 
MC-GPU includes the PENELOPE pair production cross section within the total 
cross section, and therefore the total attenuation at high energies will be ok, 
but the created electron/positron pairs and the positron annihilation photons 
are not simulated.

Original comment by diamc...@gmail.com on 9 May 2011 at 7:15