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dose rate to water at point P(r,
θ)
S
K
air kerma strength
Λ
dose rate constant
1/
r
2
geometry function (
point-source approximation
)
g
P
(
r
)
radial dose function
φ
an
(
r
)
1D anisotropy function
Rivard, et al.,
Med. Phys.
31, 633-674 (2004)
( )
D r
2
0
( )
( ) ( )
K
P
an
D r S
r g r
r
r
φ
= Λ