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A Review of TG-142 QA Results for Nine Dosimetrically Equivalent TrueBeams Over Two Years of Operation

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J Woollard

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


WE-RAM3-GePD-IT-2 (Wednesday, August 2, 2017) 10:30 AM - 11:00 AM Room: Imaging ePoster Theater

Purpose: To present the results of our TG-142 compliant monthly QA methodology for nine TrueBeams, that were commissioned as beam matched and dosimetrically equivalent, for two years of operation and to evaluate the performance of these linacs against the tolerances listed in TG-142.

Methods: Beginning December 2014 we commissioned nine TrueBeam linear accelerators, implemented identical QA processes for all machines, and established common TG-142 baselines for monthly and annual QA. All QA data is automatically stored in a SQL database. BI dashboards were implemented to provide the users with a dynamic data trending interface. The “R” statistical package within Microsoft PowerBI was used to perform statistical analysis of the filtered QA data. For this work, two years of results were mined from all nine linacs for each monthly QA test, excluding imaging QA tests, and reported an average and standard deviation for each test result. The resulting average QA test result values and standard deviation values were compared to the recommended values and tolerance values listed in TG-142.

Results: For each monthly TG-142 QA test, average and standard deviation values were calculated from our data. For example, profile constancy for in-plane profiles were found to be 0.32±0.15%, 0.34±0.10% and 0.35±0.10% for 6X, 10X and 15X respectively, while the cross-plane values were 0.34±0.14%, 0.46±0.12% and 0.42±0.17%. Our values are all well below the TG-142 tolerance value of 1%.

Conclusion: Our standard QA processes, methods, QA data storage and mining capabilities have allowed us to gain valuable insights and establish and comply with baselines and tolerance values for all parameters listed in TG-142. This data may also be useful to other facilities that wish to assess the performance of their TrueBeam linac.

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