ESTRO 2024 - Abstract Book

S4804

Physics - Quality assurance and auditing

ESTRO 2024

92.0% to 98.1%, and from 83.8% to 97.3% for the volume restricted to the PTV. For the investigated 235 adaptive treatment sessions, the average global gamma passing rate was 98.8% ± 0.6% and 98.0% ± 1.2% for the overall volume and the volume restricted to the PTV, respectively. In the evaluation of key DVH parameters, the analysis revealed that Dmean values consistently met the TPS prediction, with an average deviation of only 0.3% ± 0.4%. In the case of simultaneous integrated boost treatments, the D95% values exhibited average variations of -0.7% ± 1.1% compared to the target values. The gamma analysis and DVH metrics results demonstrated an even higher level of consistency when evaluated on a per-patient basis, reflecting the similarity of treatment plans per course, as evident from the closely aligned monitor unit numbers. Statistically derived tolerance thresholds defined by the mean value minus two standard deviations allow assessing the quality of agreement in SDC. This can provide valuable indications to identify specific adapted plans warranting closer scrutiny and investigation. Most plans that fail these tolerance levels are either highly complex or exhibit substantial changes in monitor units, exceeding a 10% difference compared to the reference plan.

Conclusion:

SDC with Mobius3D is feasible in the context of adaptive radiotherapy on Ethos. Statistically derived tolerance thresholds aid in quality assessment and anomaly identification. However, it is essential to highlight that currently no independent verification of the synthetic CT utilized for dose calculation is conducted. Utilizing more enhanced and sophisticated models and algorithms for SDC resulting in improved agreement has the potential to increase the sensitivity for detecting clinically relevant errors during oART, enhancing treatment safety.

Keywords: quality assurance, adaptation, dose calculation

1225

Digital Poster

Radiotherapy Quality Assurance over the course of time, a systematic literature review

Gaelle LE QUELLENEC 1 , Tanguy Perennec 1 , Juliette Thariat 2 , Stéphane Supiot 1

1 Institut de Cancérologie de l'Ouest, Radiotherapy, Nantes, France. 2 Centre François Baclesse, Radiotherapy, Caen, France

Purpose/Objective:

Radiotherapy quality assurance (RTQA) is a systematic process by which an RT plan’s conformity is analyzed with respect to the RT planning guidelines in the trial protocol. It is an essential step in clinical trials for ensure the reliability of the trial results. In the past, some studies have shown that protocol deviations significantly affect clinical trial outcomes and decrease overall survival. However, the RTQA process is very demanding, time consuming and requires human and technical resources. Knowing these constraints and trends, we undertook a systematic literature review and assessed RTQA trends over time and parameters influencing the type of RTQA.