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Approximations in dose calculation
Infinite slab approximation: doses at phantom boundaries
The depth (
z
) is
generally assumed to be
constant within the
lateral integration plane
during calculation of the
scatter dose to a point.
Calculatio
n point
ρ
0
Primary
depositio
n volume
z
Calculatio
n point
ρ
0
Primary
depositio
n volume
z
Scatter underestimated
Calculatio
n point
ρ
0
Primary
depositio
n volume
z
Errors cancel (roughly)
Calculatio
n point
ρ
0
Primary
depositio
n volume
z
Scatter overestimated
Calculatio
n point
ρ
0
Primary
depositio
n volume
z
Backscatter overestimated
Ideal case