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Mean energies in a 6 MV beam depending
on field size and depth
Incident mean photon
energy = 2.11 MeV
Heydarian
et al
~0.16 MeV (1/10)
~0.7 MeV (1/3)
Two counteracting effects as depth increases: Beam hardening of
primary fluence and increasing amount of scattered photons.
photons
electrons