S1978
Physics - Dose prediction/calculation, optimisation and applications for photon and electron planning
ESTRO 2026
[1] Hernández V, Vera-Sánchez JA, Vieillevigne L, Saez J. Commissioning of the tongue-and-groove modelling in treatment planning systems: from static fields to VMAT treatments. Phys Med Biol. 2017;62(16):6688-6707. https://doi.org/10.1088/1361-6560/aa7b1a Keywords: Secondary dose calculation, Monte Carlo, MLC
threshold. Results:
The optimal ARLFO values for each energy are shown in Table 1 and resulted negative across all energies. Figure 1.B shows an upward shift in median GPR of about 9 percentage points (p.p.) for 6X, 17p.p. for 6FFF, and 12p.p. for 10FFF. Statistically significant improvements were observed for 6X, 6FFF, 10FFF when using optimal ARLFO value compared to the default configuration (p<0.05). For 10X the GPR medians remained comparable (GPR_default=88.4% vs GPR_optimal=87.9%), with no significant difference (p=0.304).
Digital Poster 4109
VMAT strategies for whole breast radiotherapy: pseudo skin flash technique, replanning criteria and shoulder avoidance in nodal irradiation cases Pedro C Reis, João T Freitas, Tiago N Ribeiro, João P Galhardas, Luís M Prudêncio, Sara F Santos, Telma Coelho, Claudia D Machado, Sandra Charrua, André Figueiredo, Diogo Delgado Serviço Radioterapia, ULS Santa Maria, Lisbon, Portugal Purpose/Objective: This study outlines departmental strategies for VMAT planning in whole breast radiotherapy, with a focus on optimizing surface dose and managing nodal irradiation. Key components include:VMAT planning using split tangential arcs;Implementation of a shoulder avoidance structure for cases with supraclavicular node irradiation, preventing beam entry through the shoulder and enabling anterior- posterior arc incidence similar to 3DCRT, without increasing plan complexity;A pseudo-skin flash technique combining a virtual bolus and Auto Flash Margin (AFM) to enhance fluence robustness in the dose fall-off region;IGRT protocols and criteria for Treatment plans were created using Monaco TPS v6.1.4 (Elekta) and delivered on an Elekta Versa HD, with a standard prescription of 40.05 Gy in 15 fractions. IGRT was performed using kV-CBCT (Elekta XVI).Planning employed two split tangential semi-arcs with jaw shielding [1-4]. For cases involving supraclavicular node irradiation, a shoulder avoidance structure was applied to reduce the dose to the humeral head without increasing plan complexity.The pseudo skin flash region was achieved by combining a 1 cm virtual bolus (ED = 0.9) [3,5] with a 0.5 cm AFM. Comparisons were made with AFM-only plans to assess dose coverage and homogeneity in the fall-off region. Replanning was triggered when breast adaptive replanning. Material/Methods: displacement exceeded the virtual bolus boundary [6].All plans were normalized to V95% = 3805 cGy on the breast volume, and the virtual bolus region was evaluated. The effect of the shoulder avoidance structure was assessed by contouring and analysing a region adjacent to the humeral head. IGRT robustness
Conclusion: The analytical method developed is generalizable and can be easily adopted by other radiotherapy centres to analytically configure the ARLFO parameter, tailoring it to the clinical plan characteristics of each institution. References:
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