Speaker
Description
Introduction: Proton minibeam radiation therapy (pMBRT) enhances normal tissue sparing through sub-millimetric beamlets that create high-dose peaks and low-dose valleys. While research often utilizes a single Bragg peak, limiting treatment depth, this work addresses clinical target coverage by developing a passive Spread-Out Bragg Peak (SOBP) system specifically for radiobiological research across a target volume.
Materials and Methods: We modeled the beamline using the TOPAS Monte Carlo platform. Optimization occurred in two stages: first, refining the multi-slit collimator to produce distinct beamlets, and second, designing a mini-ridge filter to modulate proton energy. Balancing these components is technically demanding, as ridge filter scattering can blur the sharp fractionation required for effective pMBRT.
Results: The simulations proved that the integrated system successfully maintains the physical advantages of spatial fractionation while achieving SOBP. Even with the introduction of the mini-ridge filter, the characteristic "peaks and valleys" of the minibeam were preserved with a PVDR of 1.8, ensuring that the biological sparing effect remains viable in the entry region. The optimized collimator design effectively partitioned the broad beam into multiple beamlets in the shallow tissue depths, providing the necessary protection for skin and intervening healthy structures. As the protons penetrate further into the phantom, the beamlets broaden and overlap, ultimately form a uniform dose distribution across the intended target area. This demonstrates the feasibility of using passive scattering components to deliver complex pMBRT treatments in a research setting.