Physics Athens 2016

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)