Advanced Physics for Brachytherapy 2018

The problem …

• Point isotopic monoenergetic photon source in infinite medium of given composition • If I know everything there is to know about the source and the medium, can I calculate dose at a point i …?

i

i ρ enμ (= prK D prΨ)



r

ipr

i

For D the depends on: the probability of a primary photon interacting in one of a number of possible interaction types at every point of the geometry , the probability distribution determining the new direction of a photon and its energy degradation, the probability this process is repeated due to multiple scattering at every point of the geometry i sc E Ψ scat at point i need

D scat at point i, CANNOT be analytically calculated NOT because of its stochastic nature, but due to the complexity of the calculation