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1. I need to be efficient
An efficient algorithm for the
calculation of dose from 1
st
scatter:
•
Calculate S
1sc
distr., from D
prim
distr.
•
Choose ΔΩ: optimal number of
directions
•
Construct lattice of transport lines (B
θ
,
b
θ
per ΔΩ, relative to direction of
primaries)
•
Ray-trace along each transport line for
Δr
i
and iteratively calculate D
i
•
Sum D
i
from all transport lines
Input:
•
D
prim
distr.
•
Source primary spectrum for calculating
S
1sc
•
1
st
scatter kernel
•
Individual voxel density data
Assumptions:
CC:
•
S
1sc
does not vary with θ within ΔΩ (Bθ,
bθ constant along transport line)
•
S
1sc
generated, emitted and absorbed
along transport line
and:
•
S
1sc
generated per unit r is constant
within the same voxel (scerma does not
vary considerably within voxels)
1
S ρ [1 exp(
)][1 exp(
)]
1sc,i-1 i-1
1
D D
D
1sc
1sc 1
1sc
ρ
Δr
i
i
1
S {
[1 exp(
)]}
1sc,i
i
B
b r
b r
i
i
i
i
i
i i
b
b
i
b r
b r
i
i
B
b
b ri
−
− −
− −
−
=
+
=
+
− →
→
− − −
+