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KERMA vs Absorbed Dose
Absorbed Dose
: energy
absorbed
per unit mass (J/kg = Gy)
Mean energy transfer imparted by ionizing radiation to matter within volume V
KERMA
:
K
inetic
E
nergy
R
eleased per unit
Ma
ss (J/kg = Gy)
Sum of initial kinetic energies transferred from
indirectly ionizing
radiation (
) to
charged particles (e
-
) in a sample of matter
→
E(entering V) – E(leaving V)
absorption of energy does not take place at same location as energy transfer by
KERMA
→
electrons travel in the medium and deposit energy along their tracks, the subsequent
imparting of energy to matter (
absorbed Dose
) is spread over distances determined by
the ranges of charged particles