ESTRO 2025 - Abstract Book

S3150

Physics - Inter-fraction motion management and offline adaptive radiotherapy

ESTRO 2025

Results: The replication of the experiment under the original conditions demonstrated high reproducibility, with a gamma pass rate of 99%. In contrast, modelling an air cavity resulted in a gamma pass rate of 74% (Fig. 2), whereas mimicking weight gain by an additional casing yielded a gamma pass rate of 69%. The global gamma pass rate could guide the decision for required plan adaptations, whereby the gamma pass rate in specific regions of interest could be employed to localise the anatomical change.

Conclusion: This phantom study suggests that the reconstruction of attenuation images after proton irradiation is sufficient to resolve anatomical changes in patient geometries. Following the recalculation of the dose distribution, the gamma analysis can identify required plan adaptations. Therefore, a complete workflow as outlined in this study appears feasible in patient treatments and could be basis for plan adaptation.

Keywords: adaptive therapy, MLAA, proton therapy