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Differences between proton and photon
planning
Differences derived from differences in physics
– Finite and controllable depth of penetration
– Penetration of protons strongly affected by the nature of the tissue
(e.g. density)
– Proton therapy very sensitive to tissue heterogeneities
– Apparatus for proton-beam delivery is different
– For intensity modulated spot scanning proton therapy the „segments“
are defined by the spots and not by mechanical devices
– Intensity varied by number of particles in a spot (photon therapy:
fluence modulation by using small segments)
ICRU 78: Prescribing, Recording and Reporting Proton beam Therapy