Dosimetric Characteristics of Clinical Photon Beams

6 MV
Isodose Distributions
(20 X 20 Cm2 (20 X 20 Cm ) 2 )
18 MV
Note contaminant electrons contribute to dose outside the field
at shallow s a o depths. dept s The e magnitude ag tude aand d eextent te t oof dose outs outside de
the geometric edge of a field at shallow depths increases with
beam energy.