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The monitor signal caused by backscatter as a function of collimator aperture, can be
modelled as an additional fraction
b
of the direct signal. The formalism would be:
0
0
0
; , ;
; , ;
1
D A x y z D A x y z
M
b
M
A
ref
ref
ref
ref
Measured
ref
ref
ref
ref
ref
0 Calculate
0
d
0
; ,
,
1
; ,
,
D A x y z M
b A
x y z
M
D A
Dose per MU formalisms
ref
1
1
b A
b A
Explicit as a backscatter correction factor: