490 / 1359
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.