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Mean energies in a 6 MV beam
depending on field size and depth
Two counteracting effects as depth increases: Beam hardening
of primary fluence and increasing amount of scattered photons.
photons
electrons
~0.16 MeV (1/10)
~0.7 MeV (1/3)
Incident mean photon
energy = 2.11 MeV
Heydarian
et al
[2]
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