Evaluation of the usefulness of the electron Monte Carlo algorithm for planning radiotherapy with the use of electron beams

Abstract

The aim of the study was to verify the accuracy of calculations of dose distributions for electron beams performed using the electron Monte Carlo (eMC) v.10.0.28 algorithm implemented in the Eclipse treatment planning system (Varian Medical Systems). Implementation of the objective of the study was carried out in two stages. In the first stage the influence of several parameters defined by the user on the calculation accuracy was assessed. After selecting a set of parameters for which the best results were obtained a series of tests were carried. The tests were carried out in accordance with the recommendations of the Polish Society of Medical Physics (PSMP). The calculation and measurement of dose rate under reference conditions for semi quadratic and shaped fields were compared by individual cut-outs. We compared the calculated and measured percent depth doses, profiles and output factors for beams with an energy of 6, 9, 12, 15 and 18 MeV, for semi quadratic fields and for three different SSDs 100, 110, and 120 cm. All tests were carried out for beams generated in the Varian 2300CD Clinac linear accelerator. The results obtained during the first stage of the study demonstrated that the highest compliance between the calculations and measurements were obtained for the mean statistical uncertainty equal to 1, and the parameter responsible for smoothing the statistical noise defined as medium. Comparisons were made showing similar compliance calculations and measurements for the calculation grid of 0.1 cm and 0.25 cm and therefore the remaining part of the study was carried out for these two grids.In stage 2 it was demonstrated that the use of calculation grid of 0.1 cm allows for greater compliance of calculations and measurements. For energy 12, 15 and 18 MeV discrepancies between calculations and measurements, in most cases, did not exceed the PSMP action levels. The biggest differences between measurements and calculations were obtained for 6 MeV energy, for smallest fields and large SSD distances. Despite these discrepancies between calculations the model was adopted for clinical use.

Commissioning and initial validation of Eclipse eMC algorithm for the electron FLASH research extension (FLEX) system for pre‐clinical studies

“…Lastly, previous research has shown that the eMC algorithm may have limitations for lower electron energies, smaller cutout sizes, and larger SSDs and may underestimate or overestimate the absorbed dose in certain regions. 17 , 18 , 19 , 20 It is important to consider these limitations when using the eMC algorithm for FLASH treatment planning, and further research is needed for geometries and conditions not tested in this study.…”

Improvement of Calculation Accuracy in the Electron Monte Carlo Algorithm with Optional Air Profile Measurements

“…However, some limitations hinder the use of the eMC algorithm. Several studies have demonstrated discrepancies between measurements and calculations, particularly for lower electron energies, smaller applicator sizes, and larger source-to-surface distances (SSDs) [10,[12][13][14]. In the buildup region at 4 MeV, the eMC algorithm produces up to 5.4% lower absorbed dose than that of the full MC model.…”