ESTRO 2025 - Abstract Book

S3509

Physics - Optimisation, algorithms and applications for ion beam treatment planning

ESTRO 2025

Conclusion: We identified a D RBE LET d -volume constraint to reduce the healthy brain radionecrosis probability in intracranial meningioma and solitary fibrous tumour treated with IMPT. Comprehensive studies applying this constraint on larger dataset should be conducted to confirm our result.

Keywords: DLVH, LET, IMPT

References: [1]

Yang Y, Vargas CE, Bhangoo RS, Wong WW, Schild SE, Daniels TB, et al. Exploratory Investigation of Dose Linear Energy Transfer (LET) Volume Histogram (DLVH) for Adverse Events Study in Intensity Modulated Proton Therapy (IMPT). Int J Radiat Oncol Biol Phys 2021;110:1189–99. https://doi.org/10.1016/J.IJROBP.2021.02.024. [2] Iannalfi A, Riva G, Lillo S, Ciccone L, Fontana G, Molinelli S, et al. Proton therapy for intracranial meningioma: a single-institution retrospective analysis of efficacy, survival and toxicity outcomes. J Neurooncol 2024;169:683–92. https://doi.org/10.1007/S11060-024-04751-X.

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Digital Poster Combination of discrete proton arcs, shoot-through layers and upright position unlocks dosimetric advantages Erik Engwall, Victor Mikhalev, Otte Marthin, Viktor Wase Research and Development, RaySearch Laboratories, Stockholm, Sweden Purpose/Objective: Proton arcs can create highly conformal plans without non-coplanar directions 1 and are therefore suitable for delivery in upright position. Adding a layer of shoot-through (ST) protons in conventional IMPT has proven to improve plan quality by reducing the lateral penumbra of the field 2 . In this study we combine discrete proton arcs with ST layers from each arc direction (Arc+ST). Material/Methods: We investigated this principle by using the compact Mevion FIT machine (fixed beam in upright position) and created robustly optimized plans (3 mm setup/3.5% range uncertainty) in RayStation for three artificial phantom targets (box 3 cm, H-shape 4.5 cm, H-shape 6 cm; see Figure 1), as well as for a H&N cancer patient. The Mevion FIT is equipped with a dynamic collimator, which can be used to trim the spots. The Arc+ST method can be used as an alternative to the collimator to reduce the field penumbra. The plans created were (1) uncollimated Arc+ST, (2)