ESTRO 2024 - Abstract Book

S4865

Physics - Quality assurance and auditing

ESTRO 2024

7. Position accuracy analysis of the stereotactic reference defined by the CBCT on Leksell Gamma Knife® Icon™. (2015). Elekta. [White paper]

2176

Digital Poster

Implementation of a distributed PSQA model across a network of matched linear accelerators for SABR

Jonathan Dunning 1 , Leon Dunn 1 , Simon Goodall 2 , Christopher Colyer 3 , Mark Wanklyn 4 , Muhammad Aqeel Hussain 4 , Michael Jameson 4 1 GenesisCare, Physics, Melbourne, Australia. 2 GenesisCare, Physics, Perth, Australia. 3 GenesisCare, Physics, Adelaide, Australia. 4 GenesisCare, Physics, Sydney, Australia

Purpose/Objective:

Stereotactic ablative body radiotherapy (SABR) is fast becoming the standard of care for several indications [1]. It requires a high level of quality assurance due to the need for increased dosimetric precision and spatial accuracy above that required for routine radiotherapy. This includes a rigorous patient-specific quality assurance (PSQA) program. However, PSQA is resource intensive and is often performed after hours due to linac capacity. With matched machines, it is feasible to perform the QA on a matched machine other than the machine the patient will be treated on, i.e., distribute the QA to another machine. It has been shown in the literature [2,3,4] that a distributed PSQA model is possible between matched machines for highly complex SABR treatments when using a gamma criterion of 3%/2mm. Our institution operates as a network of matched machines. This project aimed to determine if it was feasible to implement a system of distributed PSQA for ‘less complex’ SABR treatment sites, such as prostate and lung. If it was shown to be feasible, we would then determine a method for onboarding linacs and establish a distributed SABR cohort of machines to increase efficiency and flexibility and make better use of machine capacity across our network.

Material/Methods:

For each treatment platform, VersaHD/Monaco® (Elekta Stockholm, Sweden) and TrueBeam®/Eclipse TM (Varian, Palo Alto, USA) 11 stereotactic plans were generated and measured using the ArcCheck® QA device (Sun Nuclear, Melbourne, USA). These plans covered a wide range of treatment sites (lung, bone and prostate), target sizes (6 103cm 3 ), complexities (1.4-3.94 MU/cGy) and included 2 ‘error plans’ that had deliberate MLC shifts introduced to the calculated treatment planning system (TPS) DICOM data used for analysis. 16 linacs (8 VersaHD and 8 TrueBeam®) delivered the plans following detailed measurement, analysis and recording instructions which included strict guidance on ArcCheck® setup. From these 176 measurements, process-based control and action limits based on AAPM TG218 guidelines [5] were then calculated, per plan, for each platform. These linacs were chosen to be an initial distributed SABR cohort.

An onboarding process was then undertaken whereby prospective linacs measured the 6 most robust plans (Gamma passing range < 5% for VersaHD and < 7% for TrueBeam®) out of the original 11 plans on the ArcCheck® following