Room: AAPM ePoster Library
Purpose: To validate an MR-compatible version of the Scandidos Delta4 Phantom+ on a 0.35T MR guided linear accelerator (MR-Linac) system.
Methods/Materials: 39 clinical treatment plans originally delivered on a 0.35T MR linac system were replanned on the MR-compatible Delta4 Phantom+ geometry following our quality assurance (QA) protocol. The QA plans were then measured using the Delta4 Phantom+ and the global gamma pass rates were compared to previous results measured using a Sun Nuclear ArcCHECK®. Both 3%/3mm and 2%/2mm global gamma pass rates with a 20% maximum dose threshold were recorded and compared.
Results: The average gamma pass rate for the groups of plans investigated was found to be slightly higher on the MR-compatible Delta4 Phantom+ system than the Sun Nuclear ArcCHECK. Both systems demonstrated similar levels of gamma pass rates at 3%/3mm. The differences between the two systems became more pronounced for the 2%/2mm gamma test with the MR-compatible Delta4 Phantom+ unit demonstrating noticeably higher gamma pass rates than the ArcCHECK system. The most highly modulated plans (which historically involved some of the lowest gamma pass rates) demonstrated slightly higher gamma pass rates on the MR-compatible Delta4 Phantom+ system than the Sun Nuclear ArcCHECK.
Conclusions: The MR-compatible version of the Scandidos Delta4 Phantom+ has been validated for clinical use on a 0.35T MR-Linac with results comparing favorably to a legacy system that has been used previously.