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TG43 FORMALISM
The
Anisotropy Function, F(r,
),
accounts for the anisotropy of dose
distribution around the source, including the effects of absorption and
scatter in the source construction and water. It gives the angular variation of
dose rate around the source at each distance due to self-filtration, oblique
filtration of primary photons through the encapsulating material, and
scattering of photons in water. It is defined as:
) ,( ) ,(
) ,( ) ,(
) ,(
0
.
0
.
rG rD
r
G rD
rF
=
) ,( )(
) , (
) ,(
) ,(
0 0
r
Frg
rG
rG
t
S rD
k
=