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4 parameters required at each depth

z

for a given photon beam

A Ahnesjö et al (1992)

Med Phys

19, 263-273

This is the PK kernel parameterization used in Helax-TMS -> Oncentra -> etc

pencil kernel parameterization:

 

primary dose scatter dose

e

e

,

z

z

a r

b r

z

z

A

B

p

r z

r

r

Monte Carlo PB kernel represented as double exponential over radius,

tabulated for depths

z.

Motivations: lateral attenuation (

a

z

,

b

z

) and cylindrical

geometry 1/

r

factor of the effective particle fluencies.