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In the UK a Radiotherapy Provider should ensure that an independent dose recalculation is carried out. This recalculation must be independent of the planning computer and independent of the person producing the computer generated plan. When Halcyon^TM was first released there was no software based patient specific quality assurance system available in the market to provide an independent pre-treatment verification, due to the beam modelling challenges presented by the Halcyon’s double stacked MLC banks and other Halcyon specific special features. Recently, Sun Nuclear (Melbourne, FL) released DoseCHECK^TM, independent 3D dose calculation software for pre-treatment verification, and PerFRACTION^TM, a 3D dose reconstruction system using the machine log-file to verify the treatment delivery. The aim of this study was to validate DoseCHECK and PerFRACTION as software based independent patient-specific QA for Halcyon.

PDDs were generated in water by the Eclipse v15.6 treatment planning system (Varian, Palo Alto) using the Analytical Anisotropic Algorithm (AAA) and DoseCHECK which uses the Collapsed Cone Convolution Superposition algorithm (CCCS) dose calculation engine. The percentage differences between the PDDs at various depths were compared. 21 patient plans produced by the Eclipse treatment planning system (TPS) which covered a range of treatment sites (Head & Neck, Thorax, Abdomen and Pelvis) were used for this study. The dose distributions produced by the Eclipse TPS were compared to the distributions calculated by DoseCHECK and PerFRACTION. The gamma pass rates (criteria 3%/3mm, global normalisation, 10% threshold), the D95% and the mean dose difference to the PTVs were used as metrics to ensure the evaluation between the treatment planning system and the independent patient verification system was acceptable.

The PDDs generated by the DoseCHECK and Eclipse TPS showed good agreement with percentage differences of <0.3% at depths beyond D_max, differences are more pronounced in the build-up region. The results of gamma analysis demonstrated an overall good agreement for the dose distributions calculated by DoseCHECK and PerFRACTION when compared against the Eclipse generated dose distributions. The mean gamma pass rate for the plans calculated by DoseCHECK and PerFRACTION were 97.5% and 97.4% respectively. The mean dose difference within the PTV and D95% for the DoseCHECK were 0.9% and 0.8% and similarly for PerFRACTION were 1.0% and 0.9% respectively.

DoseCHECK and PerFRACTION have shown good dose distribution agreement with Eclipse TPS. The result shows that DoseCHECK and PerFRACTION are both viable systems for independent dose calculations for patients being treated on the Halcyon platform in our clinic.