Dose 2016

Modelling charged particle contamination

Needed when pencil beams kernels are derived from MC simulations

4MV

24MV

Charged particle contamination kernel

The parameters α , β , and γ can be determined through fitting to the difference between measurements and calculated photon dose.

p

2

( ) ,

r z γ− β−

c

±

α=

e e zr

ρ

A Ahnesjö and P Andreo (1989) Phys Med Biol 34 , 1451-64.

Contaminant dose per incident primary photon fluence at depth z

20 × 20 cm 2

A Ahnesjö et al (1992) Med Phys 19, 263-273

5 × 5 cm 2