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Physical processes in MV photon beams
Fluence
engine
Primary
photon
energy
Photon radiant
energy exiting
the target
Treatment
head & air
Head scatter
photon energy
Interactions, predominantly in the flattening filter
Contaminant
charged
particles
Contaminant
charged
particle energy
deposition
Electron con-
tamination
dose
Patient
3
Ahnesjö and Aspradakis, PMB 44 (1999), R99-155
Dose
engine
Primary charged
particle kinetic energy
Primary
energy
deposited
Scatter photon
energy
Scatter charged
particle kinetic
energy
Scatter energy
deposited
Bremsstrahlung and
annihilation photon
energy
Bremstrahlung and
annihilation charged
particle kinetic
energy
Bremsstrahlung
plus annihilation
energy deposited
Direct beam
phantom scatter
dose
Primary
dose
Head scatter dose
Head scatter charged
particle kinetic energy
Head scatter energy
deposited
Scatter photon
Scatter charged
particle kinetic
energy
Scatter energy
deposited
Bremsstrahlung and
annihilation photon
energy
Bremstrahlung and
annihilation charged
particle kinetic
energy
Bremsstrahlung
plus annihilation
energy deposited