Dose Course 2018_Flipping book

Beam energy spectra Constrained unfolding of spectra from depth dose measured in water

Recipe: Minimize the difference between measured depth dose and spectral weighted monoenergetic Monte Carlo calculated depth dose. Explicitly consider electron contamination depth dose in the buildup region (or exclude the buildup zone from depth doses!):

  

  

  

  

electron cont

(

)

(

)

(

)

fsize depth 

ebin 

1 2 s s e e

D

, ... s s d 

d

e e



1 2 , ..., , ...

=

c

−



+

, ...

fsize depth, fsize

ebin 1 2

depth, fsize, ebin

depth

1 2

Measured depth dose, phantom scatter normalized

MC calc depth doses for monoenergetic photons

Error norm to minimize by varying parameters

Spectrum model, constrained to a “physical” shape

Electron contamination model

28

Ahnesjö & Andreo, 1989 PMB 34, p 1451-64