(Thursday, 8/2/2018) 1:00 PM - 3:00 PM
Room: Karl Dean Ballroom A1
Purpose: To support Monte Carlo calculations, electron phase-space files were released publicly for the Varian (Varian Medical. Systems, Palo Alto, CA) TrueBeam linear accelerators (linac) but none for Varian the Clinac iX linac. The aim of this study is to model the Clinac iX linac and simulate clinical electron beams which could be used for validating available electron beam dose calculation models in the planning system for cases of complex geometries and heterogeneities.
Methods: On a locally-built 40-core cluster, GATE v8.0 (www.opengatecollaboration.org) was installed and used to model particle transport through detailed linac components designed from vendor-supplied CAD drawings. The CAD models were imported into GATE using the new tessellated volume feature. Tuning parameters included initial electron mean energy, spread and spot size. Depth-dose-derived properties such as depth of 50 percent (R50), practical range (Rp) and slope (G) were iteratively used to judge the model. Validation included comparison with scanned beam profiles and depth doses as well as Gafchromic EBT3 film measurements of dose under both homogeneous and complex inhomogeneous rib phantom.
Results: Except for the first few mm in the buildup regions, modeled depth dose curves agreed with measurements within 2%/2 mm while in-plane and cross-plane profile curves were within 3%/2mm. Film dose measurements agreed well with simulated dose distributions under the heterogeneities to within 3%/2mm for >95% of evaluated points.
Conclusion: A virtual model for the Clinac iX linac was developed and verified with measurements of electron dose distributions in homogenous and a complex inhomogeneous rib phantom. On-going work involves studying the effect of using diode measurements for tuning rather than ion chamber measurements. The recorded phase-space files will be made publicly via the IAEA web-site (www-nds.iaea.org/phsp).
Keywords
Not Applicable / None Entered.
Taxonomy
TH- External beam- electrons: Monte Carlo dosimetry
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