Dose 2016

Derivation of formalism to convert ionisation in plastic to dose to water Scaling photon energy fluence

In water at a reference depth

In solid plastic at an equivalent depth

Phantoms irradiated with the same MV photon beam

z

z

eq

ref

Ψ

s

Ψ

w

Phantom scatter factors in solid phantom

( ) ( ) ref eq sp,

2   

+ +

  

( (

)

Ψ

SSD

z

r S

r z

Simplification: by keeping SSD and field size ( r ) the same for the irradiation in solid phantom:

ref

eq

=

ref

ref

,

w

)

Ψ

r z

SSD

z

r S

eq

ref

ref

ref

sp,

,

s

Seuntjens et al, 2005, Med.Phys. 32 pp2945-