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0
P P
0
,
,
P
parameters
P
P
1
0
en
1
0
0
0
e
e
i
i
n
parameterization
E
E z
z z
i
i
P z
P
E
S S
1
0
en
1
0
0
0
e
e
i
i
n
parametrization
E
E z
z z
i
i
i
S z
S
E
E
Instead of integrating over energy, the collision kerma and scerma distributions
can be calculated directly by raytracing with parameterized exponentials. Effect
of spectral changing with depth, i.e.
depth hardening
is described by means of
the hardening coefficients
P
and
S
The parameters derived using a (depth dose effective) spectrum. Only
P
and
P
are directly measurable quantities.
Heterogeneities considered by using different sets of parameters
for each tissue type, mapped by using lookup tables from the
Hounsfield numbers!
Handling the beam spectrum – depth changes
0
S S
0
,
,
S
e.g. Pinnacle, Raystation
e.g. Oncentra