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Calculation object approximations with
heterogeneities
Pencil beam kernel
Calculation
point
Primary
deposition
volume
•
z
•
ρ
0
•
ρ
1
Scatter overestimated
Calculation
point
Primary
deposition
volume
•
z
•
ρ
0
•
ρ
1
Scatter and primary
overestimated
Calculation
point
Primary
deposition
volume
•
z
eq
•
ρ
0
•
ρ
1
Scatter underestimated
Heterogeneous
slab phantom
Calculation
point
Primary
deposition
volume
•
z
eq
•
ρ
0
•
ρ
1
•
Effects of heterogeneities are generally
modelled in pencil kernel algorithms through
depth scaling along rayline (and no lateral
scaling). Correct handling of heterogeneities
requires proper 3D modelling of the
secondary particle transport.
•
ρ
1
illustrates a
low density region,
e.g. lung tissue.