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Dose deposition physics:
•
Dose is deposited through electrons set in motion by
the photon interactions
•
Mean free path between electron interaction sites is
nanometers (biomolecule size) - but the complete
electron path length can be up to 10 cm in lung, less in
other tissues
•
For fields smaller than the actual electron range, the
dose varies strongly with local density variations and
field size
•
For fields larger than the actual electron range, the
dose varies less and is simpler to calculate