ESTRO 2024 - Abstract Book

S4234

Physics - Intra-fraction motion management and real-time adaptive radiotherapy

ESTRO 2024

Purpose/Objective:

Intrafractional motion of the treatment volume can result in inaccuracies in dose delivery if not adequately managed within the radiotherapy procedure. Several motion management techniques have been innovated to mitigate the influence of intrafractional motion during radiotherapy. When the tumour position is accurately visualized and monitored on kV imaging, real-time tracking using multi-leaf collimators (MLC) becomes viable on platforms like the Radixact system integrated with the Synchrony system. In this study, we present the steps we deemed necessary for clinical introduction of a real-time MLC and jaw tracking system. Further, the results from the first patients are presented.

Material/Methods:

We identified the following steps as part of the clinical introduction: (1) finding the potential clinical benefits of the system for our clinic as well as developing a strategy to evaluate this benefit, (2) developing a training program for the clinical staff, (3) commissioning and QA testing which included assessment of accuracy and limitations of the system, (4) clinical testing and follow up on first patients. Treatment planning was performed in Raystation with 6 kV imaging angles per gantry rotation.

Results:

We hypothesized potential clinical benefit with marker-guided tracking for prostate cancer RT (42.7 Gy/7fr) and marker-less tracking for stereotactic lung cancer RT (45 Gy/3fr), and we developed a prospective protocol in which we attempt to explore PTV margin reduction (the trial is currently ongoing). In order to assess the potential margin reduction, we calculate the accumulated dose to target, geometrical accuracy, and follow the patient and physician recorded side effects.