Program Information
Surface Dose Enhancement Using Novel Hybrid Electron and Photon Low-Z Therapy Beams: Monte Carlo Simulation
C Parsons1*, D Parsons1 , J Robar1,2,3 , R Kelly1,2,3 , (1) Dept of Physics and Atmospheric Science, Dalhousie University, Halifax, Nova Scotia, (2) Dept of Radiation Oncology, Dalhousie Unviersity, Halifax, Nova Scotia, (3) Nova Scotia Cancer Centre, Halifax, NS
Presentations
TH-C-12A-10 Thursday 10:15AM - 12:15PM Room: 12APurpose:The introduction of the TrueBeam linac platform provides access to an in-air target assembly making it possible to apply novel treatments using multiple target designs. One such novel treatment uses multiple low-Z targets to enhance surface dose replacing the use of synthetic tissue equivalent material (bolus). This treatment technique will decrease the common dosimetric and set up errors prevalent in using physical treatment accessories like bolus. The groundwork for a novel treatment beam used to enhance surface dose to within 80-100% of the dose at dmax by utilizing low-Z (Carbon) targets of various percent CSDA range thickness operated at 2.5-4 MeV used in conjunction with a clinical 6 MV beam is presented herein.
Methods:A standard Monte Carlo model of a Varian Clinac accelerator was developed to manufacturers specifications. Simulations were performed using Be, C, AL, and C, as potential low-Z targets, placed in the secondary target position. The results determined C to be the target material of choice. Simulations of 15, 30 and 60% CSDA range C beams were propagated through slab phantoms. The resulting PDDs were weighted and combined with a standard 6 MV treatment beam. Versions of the experimental targets were installed into a 2100C Clinac and the models were validated.
Results:Carbon was shown to be the low-Z material of choice for this project. Using combinations of 15, 30, 60% CSDA beams operated at 2.5 and 4 MeV in combination with a standard 6 MV treatment beam the surface dose was shown to be enhanced to within 80-100% the dose at dmax.
Conclusion:The modeled low-Z beams were successfully validated using machined versions of the targets. Water phantom measurements and slab phantom simulations show excellent correlation. Patient simulations are now underway to compare the use of bolus with the proposed novel beams.
Funding Support, Disclosures, and Conflict of Interest: NSERC
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