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SU‐E‐T‐174: First Results from an Epid Based MLC QA Program on a Siemens Artiste
Author(s) -
Haering P,
Lang C,
Schwahofer A,
StahlArnsberger C,
Schwamm F
Publication year - 2011
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.3612124
Subject(s) - siemens , calibration , computer science , data set , workflow , instrumentation (computer programming) , position (finance) , nuclear medicine , computer graphics (images) , mathematics , artificial intelligence , physics , statistics , database , medicine , finance , quantum mechanics , economics , operating system
Purpose: To present first results from an Epid based MLC QA Program done on a Siemens Artiste. Methods: In September 2010 a new MLC QA program started in our institute to replace previously film based positioning tests with Epid measurements. The tests were done on a weekly basis using a scatterblock and the Artisteˈs Epid. A SSD of 100cm was chosen to allow for the full maximum field size. A nineteen 2cm stripes MLC pattern was found be an optimum. Data evaluation was done with MLCSoftepid, PTW, Germany. This tool analyses the Epid data for all pictured leafs and is intended for a comparison to a reference data set, but can also check for nominal positions, which was employed here. To validate this new method, film based tests were done in parallel, although a comparison was difficult due to a different geometry and the film size used. MLC position data derived by MLCSoftepid were analyzed and plotted for different parameters. Results: The new workflow was easy to adapt and makes film processing and scanning dispensable. Also the evaluation was simplified as data were analyzed automatically. The evaluation distinguished a somehow wrong MLC calibration for the X1 side which was immediately corrected and would have been missed from the film evaluations. In contrast to that, the overall comparison of detected to nominal MLC positions showed a characteristic trend that was not seen in the film data. Detected positions varied strongly over the field position (up to .9mm) and were also different for both MLC sides. As this effect is not reported in literature for other MLCs, this behavior might be unique to the Siemens MLC and its special leaf end design. Conclusion: Epid based MLC QA is a feasible approach even if there are some limitations in absolute leaf position detection.