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Development of a Robust Linac QA Program for Multiple Beam Matched and Dosimetrically Equivalent TrueBeams

N Gupta*, A Ayan , D DiCostanzo , M Carlson , J Woollard , Ohio State University Medical Center, Columbus, OH


(Wednesday, 8/1/2018) 10:00 AM - 10:30 AM

Room: Exhibit Hall | Forum 9

Purpose: The purpose of this work was to develop a robust QA program for nine beam matched and dosimetrically equivalent TrueBeams, to maintain and closely monitor beam matching over four years of operation.

Methods: Many health systems are acquiring multiple linacs to be commissioned as beam matched, and expecting to maintain them as dosimetrically equivalent throughout their life cycle. Initial beam matching is a relatively easy task, setting up a QA program to maintain rigorous beam matching over years of operation requires a robust QA program with appropriate monitoring and planned interventions. At our institution we commissioned nine TrueBeams as beam matched and dosimetrically equivalent in 2014. Our QA program includes: standard TG-142 baselines developed for all linacs; standardized testing, data collection and processing methodology; QA data repository for trending, mining, and dash-boarding; mining trajectory logs of all daily treatments to detect deviations for trends or deviations; robust Annual QA process including software tools to analyze the quality of continued beam data matching.

Results: Our QA program and monitoring process have allowed us to maintain beam matching over four years of operation very successfully. Our monitoring tools allow us identify and address machine parameters trending out of tolerance. Several linacs were flagged by our tools as deviating enough they needed beam steering to be brought into compliance. Our trajectory log analytics tools have allowed us to flag failing MLC motors and other deviations before reaching interlock levels.

Conclusion: Keeping multiple machines beam matched and dosimetrically equivalent requires carefully planning, a robust QA process, and needs to include monitoring tools to anticipate and intervene early to keep machines within the beam match tolerances.


Quality Assurance, Quality Control, Software


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

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