In addition to slowing down, the charged particles are also deflected through
multiple scattering events, which redirects their energy and changes their dose deposition
patterns. This scattering is enhanced in higher atomic number materials. The detailed
calculations of multiple scattering of electrons require complex analytical or Monte Carlo
methods and these have been developed elsewhere for electron beams. However,
because secondary charged particles produced by photon beams are of lower energy
than the photons and have relatively shorter ranges, a simpler treatment of electrons is
often acceptable for photon beams. In the simplest models, recoil electrons are often
assumed to be “absorbed on the spot” for low energy photon beams. For higher photon
energies, the particle ranges are significantly longer (i.e., centimeters) and the spreading
of the energy of charged particles launched by photons needs to be modeled
(Table 3).
In addition to slowing down, the charged particles are also deflected throughmultiple scattering events, which redirects their energy and changes their dose depositionpatterns. This scattering is enhanced in higher atomic number materials. The detailedcalculations of multiple scattering of electrons require complex analytical or Monte Carlomethods and these have been developed elsewhere for electron beams. However,because secondary charged particles produced by photon beams are of lower energythan the photons and have relatively shorter ranges, a simpler treatment of electrons isoften acceptable for photon beams. In the simplest models, recoil electrons are oftenassumed to be “absorbed on the spot” for low energy photon beams. For higher photonenergies, the particle ranges are significantly longer (i.e., centimeters) and the spreadingof the energy of charged particles launched by photons needs to be modeled(Table 3).
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