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Treatment head
Variable thickness attenuator
Detector
Secondary collimator
Narrow beam
x
( )
( )
( )
( )
( )
max
max
0
0
e
d
0
d
E
E x
E
E
E
R E
E
S x
S
R E E
m
−
=
E
(
)
R E
(
)
S x
E
Detector response
Energy fluence spectrum
( )
( )
,
to be solved by numerical
methods (linear algebra)
e
i
j
i
E x
j
E
i
j
i i j
i
i
S x
E
S
A
m
−
=
=
General:
Simple approach:
(neglects energy
response variations)
Beam energy spectra
Unfolding measured transmission data