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Is Machine Performance Check a Reliable QA Tool in TrueBeam Linacs?

A Rangel*, F Khan , P Chi , Trillium Health Partners/The Credit Valley Hospital, Mississauga, ON


(Sunday, 7/14/2019)  

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 DQA3™ output was -0.1 ± 0.3% with a maximum disagreement of 0.9% amongst all Linacs. The output differences compared to weekly ion chamber measurement was -0.2 ± 0.5% with a maximum of 1%. MPC’s parameter uniformity was compared to reported symmetry measured by DQA3™ and IC Profiler™; the results agreed within 0.3 ± 0.3% (maximum difference of 1.4%) and 0.8 ± 0.6% (maximum difference of 1.5%) respectively. MPC’s parameter, beam centre, agreed with DQA3™ within -0.2 ± 0.3mm (maximum 1.5mm) and with IC Profiler™ within 0 ± 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.


Quality Assurance, Quality Control, Linear Accelerator


TH- External beam- photons: Quality Assurance - Linear accelerator

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