S1965
Physics - Dose prediction/calculation, optimisation and applications for photon and electron planning
ESTRO 2026
Results: Acuros-calculated Dm,m were within 0.2% of PRIMO for all materials except bone, where Acuros overestimated the dose by 1%-2.1%. These differences were independent of bone mass density but showed a dependence on volume size, with larger discrepancies observed for smaller volumes. The primary source of discrepancy was attributed to differences in how Acuros and PRIMO handle interface dosimetry between materials with distinct atomic composition. Surrounding the evaluated volume with a shell of bone material reduced the difference from 2.1% to 0.5% (Figure 1).
Conclusion: Volume size affects the dose calculation accuracy of Acuros, compared to PRIMO MC simulations in regions containing materials with distinct atomic composition. For Dm,m in bone, smaller volumes reduce the accuracy due to enhanced interface effect on the mean dose. For Dw,m in adipose and bone, smaller volumes improve the accuracy due to lower fluence perturbation. Further corrections are required in bone to achieve Dw,m accuracy similar to that of Dm,m. References: 1Yadav, Poonam, et al. "Dosimetric evaluation of high- Z inhomogeneity with modern algorithms: a collaborative study." Physica Medica 112 (2023): 102649.2Muñoz-Montplet, Carles, et al. "Dosimetric impact of Acuros XB dose-to-water and dose-to- medium reporting modes on VMAT planning for head and neck cancer." Physica Medica 55 (2018): 107- 115.3Andreo, Pedro. "Dose to ‘water-like’media or dose to tissue in MV photons radiotherapy treatment planning: still a matter of debate." Physics in Medicine & Biology 60.1 (2014): 309.4Reynaert, Nick, et al. "On the conversion of dose to bone to dose to water in radiotherapy treatment planning systems." Physics and Imaging in Radiation Oncology 5 (2018): 26-30. Keywords: Acuros XB, Monte Carlo simulations,
Acuros-calculated Dw,m were within 0.6% of PRIMO- calculated Dw,w except for adipose and bone where differences of 2.2% and 10% were observed, respectively. These discrepancies decreased for smaller volumes (Figure 2). Fluence corrections accounting for differences in the mean excitation energy between adipose/bone and water were applied to adjust for fluence perturbations3. The assumption of each voxel acting as a Bragg-Grey cavity during the dose conversion was evaluated and additional corrections based on the large cavity theory were partially applied to bone to enhance the agreement with PRIMO4. This resulted in a difference of similar magnitude as for Dm,m, prior to the shell correction (1-2%).
Digital Poster 3940
Dosimetric comparison between Acuros XB and Anisotropic Analytical Algorithm in brain synthetic Computed Tomography Nicola Blahníková 1,2 , Sevgi Emin 3,4 , Fernanda Villegas 3,4
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