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Film Dosimetry Verification of Monte Carlo Generated Electron Treatment Plans

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S Enright

S Enright1*, A Asprinio2 , L Lu2 , (1) University of Miami, Coral Gables, Florida, (2) South Florida Radiation Oncology, Stuart, FL


SU-E-T-188 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: The purpose of this study was to compare dose distributions from film measurements to Monte Carlo generated electron treatment plans. Irradiation with electrons offers the advantages of dose uniformity in the target volume and of minimizing the dose to deeper healthy tissue. Using the Monte Carlo algorithm will improve dose accuracy in regions with heterogeneities and irregular surfaces.

Methods: Dose distributions from GafChromicâ„¢ EBT3 films were compared to dose distributions from the Electron Monte Carlo algorithm in the Eclipseâ„¢ radiotherapy treatment planning system. These measurements were obtained for 6MeV, 9MeV and 12MeV electrons at two depths. All phantoms studied were imported into Eclipse by CT scan. A 1 cm thick solid water template with holes for bone-like and lung-like plugs was used. Different configurations were used with the different plugs inserted into the holes. Configurations with solid-water plugs stacked on top of one another were also used to create an irregular surface.

Results: The dose distributions measured from the film agreed with those from the Electron Monte Carlo treatment plan. Accuracy of Electron Monte Carlo algorithm was also compared to that of Pencil Beam. Dose distributions from Monte Carlo had much higher pass rates than distributions from Pencil Beam when compared to the film. The pass rate for Monte Carlo was in the 80%-99% range, where the pass rate for Pencil Beam was as low as 10.76%.

Conclusion: The dose distribution from Monte Carlo agreed with the measured dose from the film. When compared to the Pencil Beam algorithm, pass rates for Monte Carlo were much higher. Monte Carlo should be used over Pencil Beam for regions with heterogeneities and irregular surfaces.

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