Monte Carlo Simulations of the Dose Distribution for a Novel Y-90 Disc Source for Episcleral Brachytherapy
Presentations
(Saturday, 3/26/2022) 10:30 AM - 12:30 PM [Central Time (GMT-5)]
Room: Celestin D-E
Purpose: To calculate the dose distribution using Monte Carlo simulations for a novel Y-90 disc source recently developed for episcleral brachytherapy and compare the results with experimental measurements.
Methods: Monte Carlo simulations were performed to calculate the in-water dose distribution of this novel beta source using the “GATE,” a software based on the “Geant4” Monte Carlo simulation toolkit developed by the international OpenGATE collaboration. The geometry of the Y-90 disc source, its capsule and the surrounding water medium were accurately programmed in the simulation input files. The standard Y-90 beta spectrum from ICRU 72 was used, and the physics processes for beta and photon interactions with matters were all included. The dose profile from the Y-90 disc source was measured in water with a Gafchromic EBT-3 film, the presence of which was also included in the Monte Carlo simulations. The simulated three-dimensional dose distribution was exported and compared with measured dose profile. The phase space files of the simulations were also obtained for analysis.
Results: The measured percent depth dose (PDD) curves along the axis perpendicular to the center of the Y-90 disc were constructed from the experimental and simulated data, normalized to the point at 1 mm above the source capsule. Both PDD curves agree well for the first 5 millimeters (maximum difference ?10%) but deviate from each other beyond 5 mm. Since this depth is beyond the range of the beta source, most radiation doses are deposited by the low energy bremsstrahlung contamination x-rays that might cause significant energy dependence of EBT-3 film.
Conclusion: Monte Carlo simulations were successfully performed to confirm the measured PDD curve of the novel Y-90 disc source. This simulation work, along with the experimental measurements, laid a solid foundation for characterizing the full dosimetry parameters of this source for episcleral brachytherapy applications.
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