Author: Weber, D.C.
Paper Title Page
THPOMS024 A Novel Intensity Compensation Method to Achieve Energy Independent Beam Intensity at the Patient Location for Cyclotron Based Proton Therapy Facilities 3004
 
  • V. Maradia, A.L. Lomax, D. Meer, S. Psoroulas, D.C. Weber
    PSI, Villigen PSI, Switzerland
  • V. Maradia
    ETH, Zurich, Switzerland
 
  Funding: This work is supported by a PSI inter-departmental funding initiative (Cross)
In cyclotron-based proton therapy facilities, an energy selection system is typically used to lower beam energy from the fixed value provided by the accelerator (250/230MeV) to the one needed for the treatment (230-70MeV). Such a system has drawback of 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 (230-180MeV), we use only first degrader to increase beam emittance after degrader and thus lose intensity in emittance selection collimators. For intermediate energy beams (180-100MeV) we use the combination of both degraders, whereas for low energy beams (100-70MeV), only the second degrader limits the increase in emittance. With this approach, energy-independent beam intensities can be achieved, whilst localizing beam losses around the degrader.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOMS024  
About • Received ※ 16 May 2022 — Revised ※ 13 June 2022 — Accepted ※ 13 June 2022 — Issue date ※ 14 June 2022
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THPOMS025 A Novel Method of Emittance Matching to Increase Beam Transmission for Cyclotron Based Proton Therapy Facilities: Simulation Study 3007
SUSPMF127   use link to see paper's listing under its alternate paper code  
 
  • V. Maradia, A.L. Lomax, D. Meer, S. Psoroulas, J.M. Schippers, D.C. Weber
    PSI, Villigen PSI, Switzerland
  • V. Maradia
    ETH, Zurich, Switzerland
 
  Funding: This work is supported by a PSI inter-departmental funding initiative (Cross)
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 experimentally 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.
 
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2022-THPOMS025  
About • Received ※ 16 May 2022 — Revised ※ 11 June 2022 — Accepted ※ 28 June 2022 — Issue date ※ 28 June 2022
Cite • reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)