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(
)
(
)
(
)
Field
,
,
,
,
, d d
p
D x y z
x y
x x y y z x y
=
− −
Energy
fluence
concepts:
“Pencil” beam of photons
Water phantom
“pencil” beam = point monodirectional beam
Pencil kernel
= dose pattern
caused by a pencil beam (per
amount of radiation)
Pencil kernel
Dose calculation
View the incident photon fluence as
composed (i.e. a sum) of pencil beams
Summing pencil kernels in the same way
gives dose