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Assumptions (Med. Phys. 21 p 1227-1235):
• Predominantly first order scatter
• Triangular source distribution over the *visible* filter area
- Fit parameters
c
0
and
c
1
from measured output factors.
• Correction factors for:
- Energy loss in Compton scattering.
- Klein-Nishina cross section angular variation.
• Modulate the resultant fluence if modulators are present
( ) ( )
(
)
(
)
0 1
f
C
2
0
area as
calc
filt
viewed
backward
through the
aperture
d
c c
k k
A
z
z
−
=
−
dA
(
x,y
)
(
X,Y
)
(
)
,
i
i i
i
X Y
=
Flattening filter scatter, semi-analytical approach