S1824
Physics - Dose prediction/calculation, optimisation and applications for photon and electron planning
ESTRO 2026
Results: Plan evaluation metrics included PTV coverage, OAR doses, conformity indices, monitor units, and patient- specific QA. Across the cohort, PTV coverage and OAR sparing were comparable between Halcyon and TrueBeam plans, with no statistically significant differences observed; a subset of results is shown in Figure 2. Halcyon plans demonstrated increased modulation complexity, although this did not compromise deliverability, with all QA results passing departmental criteria. The introduction of gas override structures improved dose homogeneity and reduced excessive modulation in affected cases. RapidPlan models trained on TrueBeam data successfully produced Halcyon plans meeting clinical standards.
Conclusion: This audit demonstrates that Halcyon planning with AcurosXB can be safely and effectively implemented alongside established TrueBeam AAA techniques, delivering equivalent dosimetric quality. Although Halcyon plans were more modulated, this did not affect clinical QA, and mitigation strategies such as gas overrides further improved robustness. Re-use of existing RapidPlan models provides a practical pathway for efficient and consistent integration of Halcyon planning across the department. With this knowledge the department aims to roll out AcurosXB planning more extensively. References: [1] Ojala J. (2014). Accuracy of the Acuros XB algorithm in external beam radiotherapy: a review. Int J Cancer Ther Oncol, 2(4), 020417. doi:10.14319/ijcto.0204.17.[2] Yan C. et al. (2017). Clinical implementation and evaluation of the Acuros dose calculation algorithm. J Appl Clin Med Phys, 18(5), 195–209. doi:10.1002/acm2.12149.[3] Jin P. et al. (2018). Density override in planning to mitigate GI gas effects in esophageal RT. Acta Oncol, 57(12), 1646– 1654. doi:10.1080/0284186X.2018.1518590.[4] Visak J. et al. (2021). Fast lung SBRT plan generation with KBP on Halcyon Linac. J Appl Clin Med Phys, 22(11), 54–63. doi:10.1002/acm2.13427. Keywords: Halcyon, AcurosXB, Algorithm
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