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28

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

1 2

1 2

fsize depth, fsize

ebin 1 2

depth, fsize, ebin

depth

1 2

fsize depth

ebin

, ..., , ...

c

, ...

, ...

s s e e

D

s s d

d

e e

=

+



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

Beam energy spectra

Constrained unfolding of spectra from depth dose measured in water

Measured depth

dose, phantom

scatter normalized

Spectrum model,

constrained to a

“physical” shape

MC calc depth doses

for monoenergetic

photons

Electron

contamination

model

Error norm to minimize

by varying parameters