ESTRO 2024 - Abstract Book

S4603

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

ESTR0 2024

Results:

All plans respected clinical goals, both in terms of target coverage and OARs constraints. With LET d -based optimization, brainstem LET d decreased of (1.3±0.4) and (2.0±0.7) keV/µm at 50% and 1% of the volume, respectively, on average over the patient sample. Brainstem V 30 to V 55 gradually decreased of (10.9±1.3)% to (1.0±0.4)%; with a near-to-maximum D 1% reduction of (2.2±0.6) Gy(RBE) (Figure 1). LET d -based optimized plans were more robust against RBE model uncertainty: the application of the LWD RBE model caused an average increase of (1.5±0.3)% on V D points, compared with the (4.4±0.4)% increase of dose-based plans (Figure 1).

Figure 1 Brainstem dose volume histogram of the patient presented in Figure 2 describing the V D variation for the dose-based (solid black line), dose-based LWD (dashed black line), LET d -based (solid grey line) and LET d -based LWD (dashed grey line). Highlighted areas mark the V D points analysed for the patient cohort. The average variation between fixed and variable RBE computations is also reported.