COMPARISON OF DOSE CALCULATION ALGORITHMS MONTE CARLO, AAA AND ACUROS XB IN FRACTIONATED STEREOTACTIC RADIOSURGERY PLANNING

Dose calculation algorithms differ in their calculation methods and are relevant in radiotherapy planning. In this work, three algorithms were used: Monte Carlo (MC), which uses computational models to simulate the interactions of particles with the matter, and were considered as the gold standard; AAA, which is a superposition / convolution algorithm whose modeling is separated for primary photons, scattered photons and electrons; and Acuros XB (ACX) which uses analytical methods to solve the Boltzmann transport equation, which governs the macroscopic behavior of particles in the medium. The objective of this work was to compare the behavior of MC, AAA and ACX algorithms by evaluating dosimetric parameters and dose distribution. Ten single-lesion radiosurgery with PTV volumes between 0.5-37.4cm³ were optimized in the treatment planning system (TPS) Elements using the MC algorithm. The plans were exported to TPS Eclipse, where the dose distribution was calculated using the AAA and ACX algorithms without new optimization. Plans were normalized to have the same dose at 95% of volume. The comparison was made by assessing the dosimetric parameters: conformity index (CI), homogeneity index (HI), maximum dose (Dm) and the brain volume minus PTV receiving 12Gy (V12). The correlation of the parameters with the PTV volume and their distance to the skullcap were also analyzed. Through the Kruskal- Wallis statistical test, a significant variation (p <0.05) was observed between the calculation algorithms for the HI, not being statistical significant for the CI, Dm and V12. Using peer-to-peer comparison using the Mann-Whitney test, it was observed that ACX differs from MC, whereas the comparison between AAA and MC did not differ. Through graphical analysis, it was seen a correlation between the variation of the HI and the volume of the PTV that, the smaller its volume, the greater the variation of the HI. It can be verified that the only dosimetric parameter with statistical significant difference was the HI between MC and ACX, and a graphical analysis suggests a relationship between the volume of PTV and the difference between the HI. Therefore, it can be concluded that the three algorithms have a high agreement in stereotactic radiosurgery treatments.