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Treatment head
Variable thickness attenuator
Detector
Secondary collimator
Narrow beam
x
E
Ψ
( )
S x
Beam energy spectra
Unfolding measured transmission data
27
( )
( )
( )
( )
( )
max
max
0
0
e
d
0
d
E
E x
E
E
E
R E
E
S x
S
R E E
µ
Ψ
Ψ
− ⋅
=
∫
∫
( )
R E
E
Ψ
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
µ
Ψ
∆
Ψ
− ⋅
=
⇔ =
∑
∑
142443
General:
Simple approach:
(neglects energy
response variations)