Room: ePoster Forums
Purpose: The purpose of this work is to evaluate the accuracy and precision of the Varian Machine Performance Check (MPC) on TrueBeamâ„¢ Linear accelerators as a daily output monitoring tool by comparing its measurements against our current practice in the institution.
Methods: The MPC application was run on 4 Truebeamâ„¢ Linacs over a period of 3 months while the current local QC practice were kept in place. MPC beam constancy checks include: output, uniformity and beam centre. The 6MV beam measurements from MPC were compared to daily QC tests measured with DQA3â„¢ (Sun Nuclear Corp. Melbourne, FL, USA), weekly ion chamber output measurements in solid water, monthly symmetry tests using IC Profilerâ„¢ (Sun Nuclear Corp.), and QUASARâ„¢ eQA Winston Lutz (Modus Medical Devices Inc. London, ON, CA).
Results: The difference between MPC output and DQA3â„¢ output was -0.1 Â± 0.3% with a maximum disagreement of 0.9% amongst all Linacs. The output differences compared to weekly ion chamber measurement was -0.2 Â± 0.5% with a maximum of 1%. MPCâ€™s parameter uniformity was compared to reported symmetry measured by DQA3â„¢ and IC Profilerâ„¢; the results agreed within 0.3 Â± 0.3% (maximum difference of 1.4%) and 0.8 Â± 0.6% (maximum difference of 1.5%) respectively. MPCâ€™s parameter, beam centre, agreed with DQA3â„¢ within -0.2 Â± 0.3mm (maximum 1.5mm) and with IC Profilerâ„¢ within 0 Â± 0.2mm (maximum 0.4mm). Time spent at the unit while running the MPC is short (approximately 1 min to deliver each energy and to report results of the beam check); the process requires minimal setup time as no initial alignment is required (i.e. about 2-3 mins) and minimal user intervention.
Conclusion: MPC beam constancy checks showed reasonably good agreement with local QC results over 3 month of monitoring period for the 6MV beam.