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Geometric penumbra
Dublin 2018
The source related
geometric penumbra
(10-90%) typically has
a width of 3-5 mm at
isocenter level, but
can in more extreme
cases extend up to
about 10 mm.
Particularly important
for small beams and
IMRT.
d
coll
d
iso
(SAD)
Isocenter
Y
d
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MLC penumbras