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Session: Emerging Imaging, Therapy, and Dosimetry Solutions II [Return to Session]

Utility of EPID-Based Automated Quality Assurance (AQA) Test Suite for Verifying Machine Performance Following Non-Routine Maintenance Events

J Steers1*, J DeMarco1, H Al-Hallaq2, J Mikell3, M Barnes4, G Kim5, N Gupta6, D DiCostanzo6, A Ayan6, M Perez7, J Irrer3, J Moran8, (1) Cedars-Sinai Medical Center, Los Angeles, CA, (2) The University of Chicago, Chicago, IL, (3) University of Michigan, Ann Arbor, MI, (4) Calvary Mater Hospital Newcastle, Newcastle, NSW, AU, (5) UC San Diego, La Jolla, CA, (6) The Ohio State University, Columbus, OH, (7) Northern Sydney Cancer Centre, Royal North Shore Hospital, St Leonards, NSW, AU,(8) Memorial Sloan Kettering Cancer Center, New York, NY


SU-K-202-7 (Sunday, 7/10/2022) 5:00 PM - 6:00 PM [Eastern Time (GMT-4)]

Room 202

Purpose: To assess the value of using an automated EPID test suite with machine maintenance files when investigating the adequacy of repair for linear accelerator maintenance events.

Methods: The automated quality assurance (AQA) consortium represents 21 institutions performing monthly EPID measurements analyzed using an online platform. Machine service logs can also be uploaded to the platform and plotted against AQA results. Using in-house MATLAB code, we assessed the utility of the AQA results for detecting three example non-routine service events for one linac.

Results: Event 1: Collimator jaws were recalibrated by service without informing the physicist following mylar replacement. This change was not detected during monthly QA. However, in plotting the AQA data longitudinally, there was a visible step change in Y2 jaw position compared to baseline.Event 2: Service was called after ion chamber replacement to address failing MPC isocenter size. Following collimator-axis steering, physics verified beam profiles with ICprofiler before releasing the linac for treatment. AQA results detected an expected change in transverse beam symmetry (>1%) as well as a larger than expected change in the x-position collimator center (>1mm) not detected with the ICprofiler. Event 3: BGM faults were reported for 6x fields after the target drive assembly was adjusted. Service performed beam tuning adjustments due to low dose rate on 6x and 6FFF beam energies. Multiple adjustments were made including gun delay, energy switch, and 6x beam steering. The AQA analysis correctly recorded a change from baseline the x-position collimator center (>1mm) and transverse beam symmetry (>1%).

Conclusion: This work demonstrates the value of the AQA test suite and automated analysis for post-service testing, given challenges with service hand-offs and time constraints. The online analysis tools, combined with linac XML service logs, detected both reported and unreported service events in an automated and quantitative manner.


Quality Assurance, Linear Accelerator


TH- External Beam- Photons: Quality Assurance - Linear accelerator

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