IMRT

Relative seriality model (Källman et al 1992)

Basic assumptions : • Cell survival: Poisson statistics • Normal tissue organized in serial and parallel substructures • P (non-uniform irradiation): the contribution from each step of the DVH is calculated Formal equations: for uniform irradiation: (with dose D)

( ) 50 / 1 2 ) ( DD e e DP − − = γ

for non-uniform irradiation: (D i

, D v i

, for each step of the DVH)

dose to the whole organ 50% P of complications γ steepness s relative seriality of the organ/tissue (serial organ: s =1, parallel organ s =0) ( ) ( ) s n i v s i i DP /1 1 1 1    − − = ∏ = ∆

  

P

• Parameters : D 50