Electron Monte Carlo Dose Calculation Model Dependency on Optional Applicator Specific 1D Profile

The accuracy of a calculated dose distribution compared to the actual dose administered to a patient undergoing electron radiation treatment is dependent upon the configured electron dose calculation algorithm in the treatment planning system (TPS). Configuration of the electron Monte Carlo (eMC) algorithm in the Eclipse TPS requires a variety of beam scan data. One of the required data sets is the inclusion of optional in air crossplane (CP) and inplane (IP) profiles. It is unknown if the inclusion of the optional profiles into the eMC algorithm greatly influences the output of the TPS. Two eMC algorithms were configured in Eclipse: one with the optional in air profiles and one without. CP and IP profiles of each algorithm were calculated to a statistical uncertainty of 2% and were compared to the measured data profiles at dmax for all energy and applicator combinations using gamma analysis. The greatest differences in passing rates and average gamma for the CP and IP profile comparisons corresponded to the IP profiles due to the without optional algorithm having zero data on the electron fluence in the IP. Clinical comparisons were made by defining circular targets at dmax for various energy and applicator combinations. The greatest dose difference from all clinical comparisons made was 2.55% between the two algorithms. It is recommended that extra time should be allotted when commissioning to acquire the optional in air profiles to configure the eMC algorithm which allows for greater accuracy when calculating dose distributions.