ESTRO 2024 - Abstract Book

S3391

Physics - Detectors, dose measurement and phantoms

ESTRO 2024

Keywords: FLASH radiotherapy, synchrotron, dosimetry

3078

Digital Poster

Enhancing Treatment Quality and Patient Safety: Streamlined Process Using 3D In-Vivo Dosimetry

Maximilian Grohmann, Cordula Petersen, Andrea Baehr, Manuel Todorovic, Sebastian Schäfer

University Medical Center Hamburg-Eppendorf, Department of Radiotherapy and Radiation Oncology, Hamburg, Germany

Purpose/Objective:

As modern image-guided radiotherapy techniques continue to advance, safety margins are becoming narrower, enabling the administration of higher radiation doses. This progression not only highlights the critical need for enhanced quality assurance measures but also necessitates a significant improvement in patient-specific protocols. Traditional strategies, including Pre-Treatment-QA meaurements, MonteCarlo-based Secondary-Dose-Calculation and physics chart review, fall short in their ability to identify discrepancies occurring during radiation delivery [1]. This gap underscores the urgent need for more advanced and agile solutions, ensuring that treatments are executed as planned, thus upholding patient safety throughout every phase of therapy. Addressing this, the integration of In-Vivo Dosimetry (IVD) is gaining traction, with certain European jurisdictions even making it mandatory [2,3], offering real time, session-specific dose measurements to verify treatment fidelity. However, widespread adoption of IVD remains stymied by its operational complexity and resource-intensive nature. In this evolving field, the MV/portal imaging systems, or electronic portal imaging devices (EPIDs), equipped in modern linear accelerators, are emerging as crucial tools. While their primary functions include patient positioning and Pre Treatment-QA, EPIDs present unexplored avenues for In-Vivo Dosimetry (IVD). Their proven competence in detecting deviations — from patient anatomy changes to setup mistakes, patient movements, and treatment transfer errors — is underscored in research [4–7], a notion recently emphasized in the AAPM Task Group Report 307 [8].

This study validates our clinical EPID-IVD workflow through phantom and patient study, while pioneering an automated EPID-IVD process, seamlessly integrated into everyday clinical.

Material/Methods:

The data workflow, illustrated in Fig.1, relied on custom in-house Python scripts to ensure timely availability of all files for analysis, allowing for an immediate comparison with the planned dose distribution for every treatment fraction. Another script automated the monitoring process, cataloging analysis outcomes in our database and alerting medical physicists to deviations exceeding predefined thresholds or notable inconsistencies with previous fractions. Sensitivity of the IVD method was illustrated through repeated Head&Neck irradiation of an Alderson phantom with systematic table shifts (Fig. 2), simulating shoulder misalignment. Additionally, 34 patients with 465 fractions (average 14 fractions/patient) underwent EPID IVD measurements during a trial phase, compared with TPS and IGRT results.