ESTRO 2024 - Abstract Book

S4762

Physics - Quality assurance and auditing

ESTRO 2024

The automatic deformable propagation of the GTV from the mv-phase onto the remaining phases of a 4D-CT scan using the Aria system is acceptable for clinical use as a starting-point for delineation of the final accumulated GTV structure.

Moreover, Aria performs better than Velocity, especially in terms of propagating small tumor volumes below 1.3cc, particularly when in combination with a large tumor motion, where Velocity should be used with precaution.

Keywords: deformable propagation, 4D-CT, lung-radiotherapy

614

Mini-Oral

National guidelines for QA of deformable dose mapping: Feasibility and effect on dose prescription

Laura P Kaplan 1 , Isak Wahlstedt 2 , Rasmus L Christiansen 3 , Martin S Nialsen 4 , Eliana Vasquez Osorio 5,6 , Marco Bebek 1 , Babysubashini Thisaruban 1 , Kenneth F Hofland 1 , Vladimira Horvath 1 , Miroslaw J Stelmach 1 , Lone Hoffmann 7,8 1 Zealand University Hospital, Department of Oncology, Næstved, Denmark. 2 Copenhagen University Hospital – Rigshospitalet, Department of Oncology, Copenhagen, Denmark. 3 Odense University Hospital, Department of Oncology, Odense, Denmark. 4 Aalborg University Hospital, Department of Oncology, Aalborg, Denmark. 5 The University of Manchester, Division of Cancer Sciences, Manchester, United Kingdom. 6 The Christie NHS Foundation Trust, Christie Medical Physics and Engineering, Manchester, United Kingdom. 7 Aarhus University Hospital, Department of Oncology, Aarhus, Denmark. 8 Aarhus University, Department of Clinical Medicine, Aarhus, Denmark The frequency of re-irradiation (ReRT) cases in radiotherapy (RT) is ever-increasing. Deformable dose mapping (DDM) can be used to project detailed dosimetric information of previous treatments to inform ReRT planning. However, inherent uncertainties in DDM have hindered its use in clinical practice, leading to conservative methods of summing doses from previous treatment courses. A recent workshop on DDM with representation from all Danish RT centers resulted in a set of national guidelines for patient-specific quality assurance (QA) of DDM. The aim of this study was to investigate 1) whether these QA guidelines were feasible to implement in a clinical setting and 2) if ReRT treatment decisions were affected when DDM was performed according to these guidelines. Purpose/Objective:

Material/Methods:

ReRT cases (including both curative and palliative treatments but excluding complete overlap and stereotactic treatments) in one clinic treated between April and August 2023 were evaluated for retrospective analysis. Cases in which initial dose prescriptions were changed to account for conservative rough estimates of previous doses were flagged.