Physics Athens 2016

e - disequilibrium at tissue interfaces

Soft tissue – lung interface → Less attenuation → Increase in primary beam intensity → Reduction of scattering material → Different electron transport and longer range → lateral loss of e - equilibrium NB: Higher  E → higher e - range → penumbra broadening → wider margins required to compensate for e - disequilibrium (increased dose calculation uncertainty – worst for smaller target volumes)