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Factor-based dose calculations basic dosimetric quantities
Phantom scatter factor, S
p
S
p
is the ratio of scatter factors between the actual field size c
in the phantom and that of the reference field size c
ref
, both at
the reference depth d
ref
:
( )
(
)
(
)
(
)
(
)
ref
primary
ref
ref
total
ref
primary
ref
total
p
;
;
;
;
d c D
z c D
dc D
dc D
cS
ref
=
AAPM TG 74 report, Med Phys 36 (11), 2009
S
p
describes the effects of photon scattering in the
phantom only
c
z
R
SAD
z
ref
c