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Phantoms for TPS verification and plan QA: use of solid plastics
To compare measured doses in
plastic phantoms
against doses calculated by
TPSs, the phantoms needs to be corrected represented in the TPS
For some TPSs, the HN to relative mass density calibration does not include
an assignment of HN to the density and composition of plastic materials,
because plastics area not included in the list of available materials
In such cases, to avoid systematic deviations in the dosimetric validation of
dose engines, an
effective mass density
is being assigned to the plastic
medium.
•
An implementation of such a workaround can be found in Oncentra.
•
An effective mass density as implemented in the RayStation, is
computed for all media and aims to account for any systematic errors
introduced in the assignment of mass density to CT-HN as a result of photon
attenuation in the kV energy range (CT energies)
HN to relative mass density calibration
Oncentra