Feasibility Study of Single-Gantry-Angle Proton Minibeam Lattice Radiotherapy

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MAHMOOD-THESIS-2025.pdf (4.59 MB)
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Mahmood, Rayyan L.
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https://hdl.handle.net/1853/78726
Abstract
The purpose of this project is to investigate the feasibility of Proton Minibeam Lattice Radiation Therapy (pMBLRT) in a clinical setting. The pMBLRT is a 3 dimensional version of Spatially Fractionated Radiation Therapy (SFRT). Clinical trials indicate that the highly heterogeneous dose distribution in a tumor volume delivered by SFRT could synergistically increase immunity and thus improve clinical outcomes. Multiple single-energy proton beams are simulated using Tool for Particle Simulation (TOPAS) to model Pencil Beam Scanning (PBS) with a collimator that creates an array of mini beams which delivers the lattice pattern. This was then experimentally verified at a proton therapy center. Comparing the results of these two methods will then allow one to conclude if the treatment time and efficiency is feasible for a real clinical environment. The TOPAS code was used to model a scenario in which there are multiple single-energy proton beams that go through a brass collimator having a hexagonal pattern array of 2 mm (in diameter) holes and 6 mm Center to Center (CTC) distance. This creates a 3-dimensional lattice dose pattern within the water phantom. Five proton energies were selected based on their Bragg Peak (BP) locations that are separated by a constant value so that the 3 dimensional lattice dose pattern can cover a tumor that is ranging in depth. The simulated plan was then implemented at Emory Proton Therapy Center (EPTC) with Gafchromic films placed within a solid-water phantom, allowing one to measure the dose distribution in the phantom with high spatial resolution.The results obtained from the simulation compare well with those obtained from the experiment. The results also show that the treatment time for pMBLRT to deliver a lattice dose pattern to a tumor with 15 Gy as the peak dose is approximately 12 seconds, which is clinically feasible. Therefore, from this study one can conclude that it is feasible to carry out the pMBLRT using the PBS technique in existing proton therapy centers.
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2025-07-28
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