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Flattening of the primary photon beam
Dublin 2018
The conical
flattening filter
absorbs 50-90% of the direct photons
on the central axis.
In addition, it works as a scatter source located 7-15 cm
downstream from the target, adding 5-10% at isocenter.
Steel,
Brass,
Lead...
Lateral fluence distribution
Before ff
After ff
e
-
h