Program Information
Simple and Efficient Modeling of the Varian TrueBeam Linac Using the GATE Monte Carlo Platform
B Roth1*, N Ploquin1,2 , J Wiebe3 , (1) University of Calgary, Calgary, Alberta, (2) Tom Baker Cancer Centre, Calgary, AB, (3) Roke Technologies Ltd., Calgary, Alberta
Presentations
SU-E-T-697 (Sunday, July 12, 2015) 3:00 PM - 6:00 PM Room: Exhibit Hall
Purpose: To investigate the use of the relatively new Geant4 Application for Tomographic Emission (GATE) Monte Carlo (MC) platform for radiotherapy applications, by developing a model of the Varian TrueBeam™ linac.
Methods: Multiple 6 MV phase space files were provided by Varian, serving as a simulation particle source. Modeling of the jaws and multileaf collimator (MLC) in GATE’s macro structured environment was automated through the use of an in-house developed Python program. Profiles and percentage depth doses (PDD) were compared between MC calculations, diode, ion chamber and radiochromic film measurements for six square fields ranging in size from 1 x 1 cm² to 40 x 40 cm² at five different depths. The MLC model was evaluated through comparison to radiochromic film for an “E” shaped field defined by the MLCs at two different depths.
Results: Profiles and PDDs of MC calculated values for each field size and depth were evaluated against measurements using a tight 3%/1 mm gamma criteria. It was found that 28 out of 30 square field profiles have a gamma pass rate of ≥90%, 20 of which achieved at least a 95% pass rate. All PDDs were found to have at least a 97% pass rate. When compared to film measurements, 97% and 99% of points met the gamma criteria for the MLC shaped field along the inline and crossline axes respectively, while 100% of points achieved the criteria along both axes at a depth of 50 mm.
Conclusion: GATE provides a valid, efficient and simple to use MC platform to model medical linear accelerators for the purpose of radiotherapy dose calculation.
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