Evaluation and quality assurance of the Varian Ethos Adaptive Radiotherapy system using deformable dosimetric phantoms

Online adaptive radiotherapy (ART) involves the adaptation of a treatment plan while the patient remains immobilised on the treatment couch. The presence of the patient prohibits performance of pre-treatment delivery quality assurance (QA), which would traditionally be standard practice. The new ART module for the Varian Ethos linear accelerator, which includes a secondary check system to verify adapted treatment dose calculations, is a new and therefore unproven technology.

This research aims to:

• investigate whether the system adequately and accurately adapts treatment plans to account for clinically-representative anatomical variation, using novel 3D-printed deformable dosimetric phantoms.
• investigate the net radiobiological benefit of online plan adaptation with respect to existing offline adaptation methods.
• investigate using such phantoms for quality assurance of the adaptive system in the absence of pre-treatment patient-specific QA, making recommendations for safe and efficient ART workflows.