S2036
Physics - Dose prediction/calculation, optimisation and applications for photon and electron planning
ESTRO 2026
identified. New plans were created using MCO in a local multi-criteria workflow 3, aiming to reduce the dose to OARs as much as possible, while maintaining acceptable target coverage. The MCO plans were assessed in terms of target coverage, dose to OARs, planning time, and plan complexity. A quality assurance (QA) testing method for the MCO tool was developed. Finally, a risk assessment was carried out to investigate the risks of introducing MCO into the clinical workflow. Results: Improved parotid sparing was achieved with MCO (mean reduction of 4.37 ± 4.87 Gy and 3.86 ± 3.91 Gy for the ipsilateral and contralateral parotid Dmean respectively). The trade-off of this was a mean increase in plan maximum dose of 1.06 ± 1.00 Gy, and an increase in spinal cord Dmax (37.42 ± 3.71 Gy for clinical plans vs 42.19 ± 3.22 Gy for MCO plans). It was found that the combined time for navigation space generation and deliverable plan calculation was, on average, lowest when using Native GPU (16 mins), compared to Native CPU (42 mins) or Hybrid CPU (36 mins). MCO plans were generally more complex than clinical plans, with higher average MLC speed in the MCO plans compared to the clinical plans. However, MCO plans remained deliverable according to PSQA results. Conclusion: The performance of Varian’s MCO tool was investigated for VMAT HNC planning in the Eclipse TPS. A risk assessment was carried out using a modified FMEA process. The feasibility study was completed with promising results, and the project was brought to its clinical testing phase for further refinement. References: 1 Ramaekers, Bram LT, et al. "The impact of late treatment-toxicity on generic health-related quality of life in head and neck cancer patients after radiotherapy." Oral oncology 47.8 (2011): 768-774.2 Thieke, Christian, et al. "A new concept for interactive radiotherapy planning with multicriteria optimization: first clinical evaluation." Radiotherapy and Oncology 85.2 (2007): 292-298.3 Teichert, Katrin, et al. "Targeted multi-criteria optimisation in IMRT planning supplemented by knowledge based model creation." Operations Research for Health Care 23 (2019): 100185. Keywords: MCO, treatment planning, H&N cancer
T55855083225.30VMAT56260193420.82ccVMAT88450 679712.61698IMRT47860694325.51AverageVMAT3425 9897123.67ccVMAT58246177314.10 Table 1: Plan statistics Conclusion: This proof-of-concept study demonstrates that ccVMAT optimization improves conformality and intra- target heterogeneity, at the expense of increased total delivery time. The approach presented in this study demonstrates promise and further investigation. References: 1. Spatially Fractionated Radiotherapy in the Modern Era: The Mayo Clinic Experience. Owen, D. et al. International Journal of Radiation Oncology, Biology, Physics, Volume 114, Issue 3, S862. Spatially Fractionated Radiation Therapy in Sarcomas: A Large Single-Institution Experience. Ahmed, K. et al. Advances in Radiation Oncology, Volume 9, Issue 3. 2024. 3. Physical aspects of a spatially fractionated radiotherapy technique for large soft tissue sarcomas. Borzov, E. et al. Physics and Imaging in Radiation Oncology. Volume 22. 2022. Keywords: Spatially fractionated radiotherapy, Lattice, Grid Feasibility study and commissioning of multi- criteria optimisation in head & neck VMAT planning in Eclipse Sadhbh O'Toole 1 , Orla McArdle 2 , Sinead Brennan 2 , Elaine Tyner 1 , Christina Zacharatou 1 1 Physics, St Luke's Radiation Oncology Network, Dublin, Ireland. 2 Radiation Oncology, St Luke's Radiation Oncology Network, Dublin, Ireland Purpose/Objective: The treatment of head and neck cancer (HNC) with radiation therapy commonly involves trade-offs between disease-free survival and treatment-related toxicity 1. In these treatments, target volumes are located in close proximity to multiple organs at risk (OARs). This can result in a lengthy trial and error based planning process 2. Multi-criteria optimisation (MCO) offers a way to optimise contradictory treatment planning criteria, while also speeding up the planning process. The aims of this study were to investigate the performance of Varian’s MCO tool for VMAT HNC planning compared to standard planning, and to perform a feasibility study on the implementation of MCO into clinical use. The 15.6 and 18.1 versions of Eclipse were used. Material/Methods: Eighteen bilateral HNC clinical plans, using either a 65 Gy or 70 Gy SIB technique, and containing conflicts between targets and OARs, were retrospectively Digital Poster 5201
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