Advanced Physics for Brachytherapy 2018

Equations for the transport of scerma generated at each point along a transport line

1. I need to be efficient

Δr

1

Δr

2

Under the collapsed cone approximation: • Scerma does not vary with θ within ΔΩ (Bθ, bθ constant along transport line) and scerma generated, emitted and absorbed along transport line

θ

1

θ

2

and assuming:

• Scerma generated per unit r is constant within the same voxel (scerma does not vary considerably within voxels)

Overall, exiting voxel 2:

D D D 1sc2 1sc1 2 1sc2 2 S ρ [1 exp( 1sc,1 1 B = + = → → 



S

b r − −  −

b r

{ Δr [1 exp( b − − − b

)][1 exp(

− 

2)]

Δr )}

1sc,2





1





2



2

B

+



b

b r 

b

b

ρ

Δr

2





2





2