Room: ePoster Forums
Purpose: To provide proof-of-concept, design, and optimize a multi-cuboid proton ridge filter (MCPRF) that can be used to increase Bragg peak widths in pencil beam scanning (PBS) treatments.
Methods: Monte Carlo computer simulations were performed with the capability to insert or remove the MCPRF and adjust device parameters. Pencil beams of five monoenergetic proton energies (R50 ranges of approximately 51â€“103mm in water) were simulated and dose was recorded within a water phantom containing 0.25mm3 voxels. Benchmark simulations were completed without the MCPRF in place to determine the PBS depth dose profiles and establish the FW80M. From these simulations Bragg peak weightings and filter thickness could be determined theoretically to ascertain optimal parameters for the MCPRF. In subsequent MCPRF simulations, depth dose profiles were analyzed to quantify the impact of the MCPRF on the Bragg peak FW80M, while lateral and 2D dose profiles were compared to those without the MCPRF to ascertain any unintended impact to spot size, spot shape or range uniformity.
Results: Results for 80â€“118 MeV indicate that the MCPRF was effective at increasing the Bragg peak FW80M. As compared to the baseline, the optimal MCPRF parameter combination for our application demonstrated increases in the Bragg peak FW80M of 78%, 52%, 31%, 25%, and 16% for 80MeV,90 MeV, 100MeV, 110MeV, and 118MeV, respectively, while maintaining a stable and clinically acceptable depth dose profile and beam spot size and shape.
Conclusion: Results suggest that the MCPRF is an effective two-step range modulator that can increase the Bragg peak FW80M by up to 78% in the energy range of 80â€“118MeV. Such increases may be useful in minimizing PBS treatment times and improving beam delivery efficiency, especially for shallow targets. The MCPRFâ€™s ability to be removed and located in close proximity to the patient maximizes its clinical versatility.
Funding Support, Disclosures, and Conflict of Interest: This project was sponsored by funding from the Del E. Webb Foundation.