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Analysis of the Elekta Agility MLC Performance Using High Resolution Log Files

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C Kabat

C Kabat1*, A Alexandrian1 , D Defoor1 , P Myers2 , N Kirby1 , N Papanikolaou1 , S Stathakis1 , (1) University of Texas HSC at San Antonio, San Antonio, Texas, (2) Baylor College of Medicine, Houston, Texas


SU-I-GPD-T-366 (Sunday, July 30, 2017) 3:00 PM - 6:00 PM Room: Exhibit Hall

Purpose: With the advent of VMAT and IMRT, a requirement for more elaborate tracking techniques to monitor linac components' integrity is important. Elekta log files contain events generated every 40 milliseconds, which allow for analysis and identification of subtle changes, providing another means of quality assurance. Being able to track machine components with log files provides monitoring of treatment fractions and machine reliability. Acknowledging this, research aims were to evaluate Elekta log file utilization for linac MLC QA effectiveness and benefit.

Methods: Six MLC test patterns were constructed to review kinematic parameters of the Elekta MLC system, including gravitational effects. Each test was run five times at multiple collimator and gantry angles to obtain averages. A total of four Elekta machines were employed throughout the study. Plans were delivered using iCOMcat software and recorded log files were extracted. Log files were reformatted in Matlab and analyzed.

Results: Elekta’s Agility MLC system has shown to be capable of producing motions of 5 mm/sec to 35 mm/sec, with MLC step and shoot plans having positional repeatability averaging 0.03 mm without gravity’s effect and 0.08 mm with. IMRT represented tests showed averages of 0.5 mm for tests with and without gravity. Maximum speed RMSE for the MLC system was shown to average 0.8 mm at 35mm/sec. Acceleration tests showed less dose within turnaround regions that experience large accelerations.

Conclusion: Utilizing log files has demonstrated an ability for higher precision of MLC motions to be reviewed, based on the performance tests that were instituted. Log files provided insight on effects of friction, acceleration, gravity with MU’s deposited that previously could not be reviewed in such detail. Based on our results, log file based QA has supported our abilities to review performance and QA the functionality of Elekta’s MLC system.

Funding Support, Disclosures, and Conflict of Interest: This work has been supported in part by CPRIT Training Grant (RP170345) and Elekta.

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