Room: Exhibit Hall
Purpose: To provide proof of concept and optimize a multi-wire proton ridge filter (MWPRF) that can be used to increase the Bragg peak width in pencil beam scanning (PBS) treatments.
Methods: Monte Carlo computer simulations were performed with the capability to insert or remove the MWPRF and adjust bar width, bar spacing, and filter thickness (FT) of the device. 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 0.25mmÂ³ voxels. Benchmark simulations were completed without the MWPRF in place to determine the PBS depth dose profiles and establish the FW80M. From these simulations the relative Bragg peak weightings and FT could be determined theoretically to ascertain optimal parameters for the MWPRF. In subsequent MWPRF simulations, depth dose profiles were analyzed to quantify the impact of the MWPRF on the Bragg peak FW80M, while lateral and 2D dose profiles were compared to those without the MWPRF to ascertain any unintended impact to spot size, spot shape, or range uniformity.
Results: Our initial results for 90MeV indicate that the MWPRF was effective at increasing the PBS Bragg peak FW80M. Without the MWPRF the FW80M was 1.64mm, while the application of the MWPRF almost doubled the FW80M to 3.05mm, which was within 0.15mm (<1 voxel) of the theoretical prediction. Additionally, the increase in the FW90M was larger than a factor of two with the application of the MWPRF for all 90MeV conditions tested.
Conclusion: The results presented here suggest that the MWPRF could be a useful device in PBS treatments, by widening the Bragg peak and minimizing the number of layers necessary for clinically acceptable dose delivery. The MWPRFâ€™s ability to be removed and located in close proximity to the patient maximizes its clinical versatility.
Funding Support, Disclosures, and Conflict of Interest: Funding for this project was provided by the Del Webb Foundation.