The
capability of the TrueBeam treatment system to deliver step and shoot IMRT
plans at low dose rates was evaluated. Beam characteristics during low dose
rates (5 to 100 MU/min) were evaluated for consistency using a planar ion
chamber array. MU constancy, linearity, and beam profile symmetry were all
found to be equivalent within 0.5%. The response of the Scandi Dos Delta 4
system was also evaluated at low dose rates of using static open beams compared
to ion chamber measurements, and step and shoot IMRT plans comparing 5 - 20
MU/min and 100 MU/min dose rates, with a maximum observed absolute dose
difference of 0.8% and equivalence margin of 0.2%. The Gamma Index and
measurement reproducibility were also found to be equivalent.
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