Application of a scattering foil to increase beam transmission for cyclotron based proton therapy facilities

Maradia, Vivek; Meer, D.; Weber, Damien Charles; Lomax, Anthony; Schippers, Jacobus Maarten; Psoroulas, S.

doi:10.3389/fphy.2022.919787

Cited by 6 publications

(6 citation statements)

References 23 publications

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“…Currently, all cyclotron-based proton therapy facilities transport a maximum emittance of 30 π mm mrad through the beamline (in this work, beam sizes, divergences, and emittances are expressed as 2σ values), which limits the transmission of low-energy beams. At PSI for example, for the lowest energies (70-100 MeV), transmission through the beamline is below 0.1 % [8]. Such low transmission for these low energies causes an increase in beam-on time.…”

Section: Introductionmentioning

confidence: 99%

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A novel method of emittance matching to increase beam transmission for cyclotron-based proton therapy facilities: simulation study

Maradia

Meer

Weber

et al. 2023

J. Phys.: Conf. Ser.

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In proton therapy, high dose rates can reduce treatment delivery times, allowing for efficient mitigation of tumor motion and increased patient throughput. With cyclotrons however, high dose rates are difficult to achieve for low-energies as, typically, the emittance after the degrader is matched in both transversal planes using circular collimators, which does not provide an optimal matching to the acceptance of the following beamline. Transmission can however be substantially improved by transporting maximum acceptable emittances in both orthogonal planes, but at the cost of gantry angle-dependent beam shapes at isocenter. Here we demonstrate that equal emittances in both planes can be recovered at the gantry entrance using a thin scattering foil, thus ensuring gantry angle-independent beam shapes at the isocenter. We demonstrate in simulation that low-energy beam transmission can be increased by a factor of 3 using this approach compared to the currently used beam optics, whilst gantry angle-independent beam shapes are preserved. We expect that this universal approach could also bring a similar transmission improvement in other cyclotron-based proton therapy facilities.

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Section: Introductionmentioning

confidence: 99%

“…One way to achieve higher intensity beams at the isocenter is to transport a higher emittance through the following beamline and gantry [8][9][10][11]. At our facility, we can transport a maximum of ~65 π mm mrad in X-plane and ~139 π mm mrad in Y-plane.…”

Section: Introductionmentioning

confidence: 99%

A novel method of emittance matching to increase beam transmission for cyclotron-based proton therapy facilities: simulation study

Maradia

Meer

Weber

et al. 2023

J. Phys.: Conf. Ser.

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“…17 A recent study has demonstrated a concept of incorporating a momentum cooling design in the energy selection system to reduce the momentum spread of the beam without introducing substantial beam losses, which allows delivering proton beams at FLASH dose rates, while maintaining the necessary energy modulation. 18 To achieve FLASH delivery without modifying the current cyclotron gantry design,a potential solution is to utilize the highest energy beam for FLASH planning, bypassing the need for the inefficient energy modulation system. Efforts have been made to employ high-energy proton transmission beams (TBs) to cover the target with the entrance dose region while delivering BPs outside the patient, demonstrating feasibility in attaining the FLASH effect.…”

Section: Introductionmentioning

confidence: 99%

Streamlined pin‐ridge‐filter design for single‐energy proton FLASH planning

Ma,

Zhou,

Chang

et al. 2024

Medical Physics

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BackgroundFLASH radiotherapy (FLASH‐RT) with ultra‐high dose rate has yielded promising results in reducing normal tissue toxicity while maintaining tumor control. Planning with single‐energy proton beams modulated by ridge filters (RFs) has been demonstrated feasible for FLASH‐RT.PurposeThis study explored the feasibility of a streamlined pin‐shaped RF (pin‐RF) design, characterized by coarse resolution and sparsely distributed ridge pins, for single‐energy proton FLASH planning.MethodsAn inverse planning framework integrated within a treatment planning system was established to design streamlined pin RFs for single‐energy FLASH planning. The framework involves generating a multi‐energy proton beam plan using intensity‐modulated proton therapy (IMPT) planning based on downstream energy modulation strategy (IMPT‐DS), followed by a nested pencil‐beam‐direction‐based (PBD‐based) spot reduction process to iteratively reduce the total number of PBDs and energy layers along each PBD for the IMPT‐DS plan. The IMPT‐DS plan is then translated into the pin‐RFs and the single‐energy beam configurations for IMPT planning with pin‐RFs (IMPT‐RF). This framework was validated on three lung cases, quantifying the FLASH dose of the IMPT‐RF plan using the FLASH effectiveness model. The FLASH dose was then compared to the reference dose of a conventional IMPT plan to measure the clinical benefit of the FLASH planning technique.ResultsThe IMPT‐RF plans closely matched the corresponding IMPT‐DS plans in high dose conformity (conformity index of <1.2), with minimal changes in V7Gy and V7.4 Gy for the lung (<3%) and small increases in maximum doses (Dmax) for other normal structures (<3.4 Gy). Comparing the FLASH doses to the doses of corresponding IMPT‐RF plans, drastic reductions of up to nearly 33% were observed in Dmax for the normal structures situated in the high‐to‐moderate‐dose regions, while negligible changes were found in Dmax for normal structures in low‐dose regions. Positive clinical benefits were seen in comparing the FLASH doses to the reference doses, with notable reductions of 21.4%–33.0% in Dmax for healthy tissues in the high‐dose regions. However, in the moderate‐to‐low‐dose regions, only marginal positive or even negative clinical benefit for normal tissues were observed, such as increased lung V7Gy and V7.4 Gy (up to 17.6%).ConclusionsA streamlined pin‐RF design was developed and its effectiveness for single‐energy proton FLASH planning was validated, revealing positive clinical benefits for the normal tissues in the high dose regions. The coarsened design of the pin‐RF demonstrates potential advantages, including cost efficiency and ease of adjustability, making it a promising option for efficient production.

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“…At PSI, for example, for the highest energies (200-230 MeV), transmission through the beamline is about 30 %. However, for the lowest energies (70-100 MeV), transmission through the beamline is below 0.1 % [2][3][4][5].…”

Section: Introductionmentioning

confidence: 99%

A novel intensity compensation method to achieve energy independent beam intensity at the patient location for cyclotron based proton therapy facilities

Maradia

Meer

Weber

et al. 2023

J. Phys.: Conf. Ser.

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In cyclotron-based proton therapy facilities, an energy selection system is typically used to lower the beam energy from the fixed value provided by the accelerator (250/230 MeV) to the one needed for the treatment (230-70 MeV). Such a system has the drawback of increase beam emittance and introducing an energy-dependent beam current at the patient location, resulting in energy dependent beam intensity ratios of about 103 between high and low energies. This complicates treatment delivery and challenges patient safety systems. As such, we propose the use of a dual energy degrader method that can reduce beam intensity for high-energy beams. The first degrader is made of high Z material and the second is made of low Z material and are placed next to each other. For high energies (190-230 MeV), we use only the first degrader to increase beam emittance after the degrader and thus lose intensity in the emittance selection collimators. For intermediate energy beams (110-190 MeV) we use the combination of both degraders, whereas for low energy beams (70-110 MeV), only the second degrader limits the increase in emittance. With this approach, energy-independent beam intensities at the patient location can be achieved, whilst localizing beam losses around the degrader.

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Application of a scattering foil to increase beam transmission for cyclotron based proton therapy facilities

Cited by 6 publications

References 23 publications

A novel method of emittance matching to increase beam transmission for cyclotron-based proton therapy facilities: simulation study

A novel method of emittance matching to increase beam transmission for cyclotron-based proton therapy facilities: simulation study

Streamlined pin‐ridge‐filter design for single‐energy proton FLASH planning

A novel intensity compensation method to achieve energy independent beam intensity at the patient location for cyclotron based proton therapy facilities

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