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Basic Theorems and Principles
Absorbed dose
is the mean energy transfer imparted by ionizing radiation
to matter with volume V
Mean energy transfer = E(entering V) – E(leaving V)
KERMA
: kinetic energy transferred per unit mass (J/kg = Gy) from photons
to charged particles (electrons)
Charged particles (created by primary photons) transfer some of
kinetic energy to medium -> absorbed dose and lose some of their
energy in the form of radiative losses (bremsstrahlung, etc)
Because electrons travel in the medium and deposit energy along
their tracks,
absorption of energy does not take place at same
location as energy transfer by KERMA (Energy transfer from
indirectly ionizing radiation to directly ionizing)