A novel mono-energy proton arc therapy with patient specific range shifter for fast treatment delivery

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2024

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AbstractIntroduction:This study evaluates a new proton therapy filter designed to eliminate the need for energy adjustments. Utilizing the machine's maximum energy, the filter ensures sufficient tumor coverage through the Bragg-peak, potentially improving treatment efficiency by shortening delivery time. Methods:Implemented on the matRad platform, each plan utilized a single arc composed of 72 beams, each spaced 5 degrees apart. Open-access datasets, including TG-119 C-shape, a prostate case, and a liver case, were employed. The prescribed doses for these cases were 50Gy in 25 fractions, 68Gy in 34 fractions, and 45Gy in 25 fractions, respectively. Simplifying from multiple energy layers to a single energy layer for each beam can reduce treatment delivery time. Maintaining spot coverage with a single energy layer for each beam is a critical optimization aspect. The spot coverage, P(i,j), is optimized to maximize spot coverage and the optimization is called mono energy optimization. However, considering spot coverage alone is insufficient; the energy level must also be considered. Higher energy levels indicate a thinner range shifter, which reduces scatter and attenuation caused by range shifters. The new optimization process, called higher mono energy optimization, gave priority to deeper layers and larger spot sizes, using a function that normalizes input energy and combines it with alpha and beta coefficients to optimize the energy function E(i,j) and spot coverage P(i,j). The optimal energy layers were selected, and the initial beam energy was set at 236MeV. All beamlet was adjusted to specific energy levels with a custom-designed PMMA filter based on stopping power, facilitating a smooth transition to the desired energy levels. The effectiveness of this approach was evaluated by comparing dose metrics with those from the Intensity Modulated Proton Therapy (IMPT) method using two or three beams. Results: PTV coverages were relatively close between the IMPT and range filter plans. Organs at Risk (OAR) experienced a dose increase due to enhanced scattering. Simulated treatment delivery times for the three tested range filter plans demonstrated the efficiency, with prostate at 360s, liver at 340s, and TG119 at 390s. Conclusions: Mono-energy with range filters proton therapy is a feasible approach for expediting treatment delivery without compromising the quality of the treatment plan.

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Zhou, Yuyin (2024). A novel mono-energy proton arc therapy with patient specific range shifter for fast treatment delivery. Master's thesis, Duke University. Retrieved from https://hdl.handle.net/10161/31080.

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