(Sunday, 7/12/2020) [Eastern Time (GMT-4)]
Room: AAPM ePoster Library
Purpose:
Quality control of multileaf collimator (MLC) for RapidArc are critical and time-consuming. The purpose of this work was to develop an XML sequence to automate this task.
Methods:
A TrueBeam STx v2.7 equipped with EPID aS1200 (Varian) with developer mode capability and Microsoft Visual Studio 2019 development environment were used for the generation of XML files.
Four QA Tests for MLC were automated: T1-Static Picket Fence (0 °, 90 °, 180 °, 270 °), T2-Picket Fence during RapidArc (179 to 181 °), T3-Gantry Speed and T4-MLC Speed. The control point (CP) of T1 test contain leafs movements and monitor units (UMs) for four static gantry angles and T2 test uses variable gantry angles for each CP. Both tests were programmed with a constant dose rate of 600 UM/min. For T3 and T4 tests two stages were generated: static field and gantry movement by CP following the “Trajectory functions” where dose rate varies between CP. The difference between MUs and gantry positions generate the gantry speed and dose rate variation. Test T3 and T4 have seven and four bands respectively, where dose rate, gantry speed and leafs for each band are varied. Images obtained are saved in DICOM format on disk network for analysis by RIT software. All automated controls were verified by comparison with manual controls and excution times in each control were recorded and analyzed.
Results:
The results obtained do not show a significant difference between automatic and manual QA. The automatic and manual QC were done in 10.3±2.2 min and 17.5±5.2 min respectivelly.
Conclusion:
The developer mode in TrueBeam allows the automation of MLC QC for VMAT treatment.
Keywords
Taxonomy
TH- External Beam- Photons: Quality Assurance - IMRT/VMAT
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