ESTRO 2024 - Abstract Book

S3525

Physics - Dose prediction, optimisation and applications of photon and electron planning

ESTRO 2024

brainstem, and chiasm in favor of the HA technique. Moreover, the HA plans resulted in 65% fewer monitor units (MUs) than VMAT plans.

Conclusion:

The study demonstrates that the HyperArc technique is a comparable alternative to volumetric modulated arc therapy for treating patients with 10 or more brain metastases with a single isocenter, it was found to provide a better sparing of organs at risk and a reduced volume of brain receiving lower doses, as well as fewer MUs. The results of this study can help guide clinical decision-making for treating multiple brain metastases.

Keywords: hyperarc, brain metastases

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Proffered Paper

Individualised dose mapping uncertainty estimation for head and neck cancer re-irradiation.

Chelmis M. Thiong'o 1 , Ane Appelt 2 , Marcel van Herk 1,3 , Matthew Lowe 1,4 , David Thomson 1,5 , Eliana M. Vasquez Osorio 1,3 1 The University of Manchester, Division of Cancer Sciences, Manchester, United Kingdom. 2 University of Leeds, Leeds Institute of Medical Research at St James’s, Leeds, United Kingdom. 3 The Christie NHS Foundation Trust, Radiotherapy Related Research, Manchester, United Kingdom. 4 The Christie NHS Foundation Trust, Christie Medical Physics and Engineering, Manchester, United Kingdom. 5 The Christie NHS Foundation Trust, Clinical Oncology, Manchester, United Kingdom

Purpose/Objective:

Deformable image registration (DIR) is an important tool to enable the assessment of prior radiation doses in the re-irradiation (reRT) setting. However, the effect of geometric uncertainties on dose mapping from previous treatments onto the reRT planning scan remains a key challenge, which limits its clinical application (1) . We propose an individualised approach to quantifying geometric and dosimetric uncertainties in the dose mapping process of re-irradiation using a commercially available treatment planning system (TPS), RayStation, Version 11B-R, RaySearch Lab, Stockholm, Sweden).

Material/Methods:

Data were available for eight patients with head and neck cancer (HNC) who underwent re-irradiation. To ensure consistency of organs at risk (OAR) delineation, both the initial and reRT planning CT scans were automatically segmented using Limbus.AI v 1.7.0-B3, resulting in 26 OARs common for all patients. Planning CTs, dose distributions and contours for the initial and reRT courses were imported into RayStation.

Figure 1 summarises our method. First, DIR was performed between the initial and reRT planning CTs aiming at mapping the initial dose distribution to the reRT scan. We varied the rigid registration (RIR) initialisation (either