Dose 2016

Derivation of formalism to convert ionisation in plastic to dose to water Derivation of depth (distance) scaling factor

s   

  

ρ µ

( ) ρ

s

vs

we

w

Ratio of electron densities good approximation for 4MV.

For some materials energy dependence up to 4%

For the clinical x-ray beams scaling by the electron density ratio is not a good approximation.

Fujita etal 2010 Radiat. Res. 51 707-