ESTRO 2023 - Abstract Book

S465

Sunday 14 May 2023

ESTRO 2023

Conclusion The AT can streamline the RT planning process, increasing efficiency and time savings. Multicentric validations should be performed to assess the efficacy and simplify the clinical implementation of automatic tools in centres without dedicated teams. This work was supported by grant GR-2019-12370739. PD-0583 Challenges in modelling the Agility multileaf collimator in TPSs and current needs for improvement V. Hernandez 1 , A. Angerud 2 , E. Bogaert 3 , M. Hussein 4 , M. Lemire 5 , J. Garcia-Miguel 6 , J. Saez 7 1 Hospital Universitari Sant Joan de Reus, Medical Physics, Reus, Spain; 2 RaySearch Laboratories AB, R&D, Stockholm, Sweden; 3 Ghent University Hospital and Ghent University, Radiation Oncology, Ghent, Belgium; 4 National Physical Laboratory, Metrology for Medical Physics Centre, Teddington, United Kingdom; 5 CIUSSS de l'Est-de-l'Ile-de-Montreal, Medical Physics, Montreal, Canada; 6 Consorci Sanitari de Terrassa, Radiation Oncology, Terrassa, Spain; 7 Hospital Clinic de Barcelona, Radiation Oncology, Barcelona, Spain Purpose or Objective The goals of this study were to investigate the challenges faced when modelling the Agility MLC in commercial TPSs, how they relate to the variability found in the MLC parameters used by the community, and to explore how the implemented MLC models could be improved in the future. Materials and Methods Four Elekta linear accelerators from different centres, all equipped with the Agility MLC, were evaluated. Three centres used the RayStation TPS and one used Monaco. For comparison purposes, data from four Varian linear accelerators with the Millennium 120 MLC were also included. Average doses measured with asynchronous sweeping gap (aSG) tests (Fig 1a) were used to characterize and compare the characteristics of the Millennium and the Agility MLCs and to assess the MLC model in the TPSs. The FOURL test included in the ExpressQA package, provided by Elekta, was also used to evaluate the tongue- and-groove with radiochromic films. Finally, raytracing was used to investigate the impact of the MLC geometry and to understand the results obtained for each MLC. Results The geometry of the Agility produces dosimetric effects associated with the rounded leaf end up to a distance 20mm away from the leaf tip end measured at the isocenter plane. This affects the tongue-and-groove shadowing, which progressively increases along the distance to the tip end. This can be quantified by the average doses for the aSG tests and their decrease as a function of s (Fig 1b).