TUB —  Cyclotron Applications: Medical   (24-Sep-19   10:50—12:10)
Chair: A. Denker, HMI, Berlin, Germany
Paper Title Page
Status of the Development of a Fully Iron-free Cyclotron for Proton Beam Radiotherapy Treatment  
  • D. Winklehner
    MIT, Cambridge, Massachusetts, USA
  • L. Bromberg, J.V. Minervini, A. Radovinsky
    MIT/PSFC, Cambridge, Massachusetts, USA
  Funding: This work was supported by the US Department of Energy under award number DE-SC0013499.
Superconducting cyclotrons are increasingly employed for proton beam radiotherapy treatment. The use of superconductivity in a cyclotron design can reduce its mass by an order of magnitude and size by a factor of 3-4 over conventional resistive magnet technology, yielding significant reduction in overall cost of the device, the accelerator vault, and its infrastructure. In the presented work, we go a step further and remove the iron yoke, generating the magnetic field with a combination of superconducting coils only. Eliminating the iron yoke has two key benefits. First and foremost, the overall weight can be reduced by almost another order of magnitude. Secondly, eliminating all magnetic iron from the flux circuit results in a linear relationship between field and coil current, which allows smooth scaling of the magnetic field and thus the output energy, thereby removing the need for a degrader. Here we describe the status of the design of such an iron-free cyclotron, currently under development at the Plasma Science and Fusion Center at MIT, with coil and cryostat calculations as well as beam dynamics studies and treatment plan considerations pertaining to this type of cyclotron.
slides icon Slides TUB01 [5.954 MB]  
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  • O. Karamyshev, K. Bunyatov, S. Gurskiy, G.A. Karamysheva, D.P. Popov, G. Shirkov, S.G. Shirkov, V.L. Smirnov, S.B. Vorozhtsov
    JINR, Dubna, Moscow Region, Russia
  • V. Malinin
    JINR/DLNP, Dubna, Moscow region, Russia
  Physical design of the compact superconducting cyclotron SC230 (91.5MHz) has been performed. The cyclotron can deliver up to 230 MeV beam for proton therapy and medico-biological research. As the cyclotron will have a relatively small magnet field, it is possible to use both superconducting and resistive coil. Besides a superconducting cyclotron we simulate design of the cyclotron with a conventional copper water-cooled coil. Such a solution allows us to achieve a lower price compared to superconducting options, but it becomes a bit heavier.  
slides icon Slides TUB02 [8.397 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-Cyclotrons2019-TUB02  
About • paper received ※ 15 September 2019       paper accepted ※ 26 September 2019       issue date ※ 20 June 2020  
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TUB03 MRI-Guided-PT: Integrating an MRI in a Proton Therapy System 144
  • E. van der Kraaij, J. Smeets
    IBA, Louvain-la-Neuve, Belgium
  • L. Bertora, A. Carrozzi, A. Serra
    ASG, Genova, Italy
  • S. Gantz, A. Hoffmann, L. Karsch, A. Lühr, J. Pawelke, S. Schellhammer
    OncoRay, Dresden, Germany
  • B. Oborn
    CMRP, Wollongong, Australia
  Integration of magnetic resonance imaging (MRI) in proton therapy (PT) has the potential to improve tumor-targeting precision. However, it is technically challenging to integrate an MRI scanner at the beam isocenter of a PT system due to space constraints and electromagnetic interactions between the two systems. We assessed the technical risks and challenges, and present a concept for the mechanical integration of a 0.5T MRI scanner (ASG MR-Open) into a PT gantry (IBA ProteusONE). Finite element simulations assess the perturbation of the gantry’s elements on the homogeneity of the scanner’s static magnetic field. MC simulations estimate the effect of the scanner’s magnetic field on the proton dose deposition. To test the technical feasibility, a first experimental setup was realized at the PT center in Dresden, combining a 0.22T open MRI scanner with a static proton beam line. Results show that the image quality is not degraded by proton beam irradiation if the acquisition is synchronized with beam line operation. The beam energy dependent proton beam deflection due to the scanner’s magnetic field is significant and needs to be corrected for in treatment planning and dose delivery.  
slides icon Slides TUB03 [1.866 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-Cyclotrons2019-TUB03  
About • paper received ※ 14 September 2019       paper accepted ※ 26 September 2019       issue date ※ 20 June 2020  
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TUB04 On-Line Dynamic Beam Intensity Control in a Proton Therapy Cyclotron 148
  • S. Psoroulas, P. Fernandez Carmona, D. Meer, D.C. Weber
    PSI, Villigen PSI, Switzerland
  • D.C. Weber
    KRO, Bern, Switzerland
  • D.C. Weber
    University of Zurich, University Hospital, Zurich, Switzerland
  Modern proton therapy facilities use the pencil beam scanning (PBS) technique for the treatment of tumours: the beam is scanned through the tumour volume sequentially, i.e. stopping the beam at each position in the tumour for the amount of time necessary to deliver the prescribed dose for that position, and then moving to the next position (dose-driven delivery). This technique is robust against fluctuations in the beam current. Modern cyclotrons however offer very stable beam currents, and allow regulating the beam intensity online to match the requested beam intensity profile as a function of time (’time-driven’ delivery). To realise time-driven delivery at the COMET cyclotron at PSI*, we have designed a beam intensity controller** which is able to partially compensate for the non-linearity and the delay introduced by the physical limitations of the beam line elements and its drivers; this is particularly important when trying to achieve a very fast modulation of the beam, as required by the clinical plans. Experimental results have shown good performance for most current clinical scenarios, though we are investigating more advanced solutions for higher dose rates scenarios.
(*) Klimpki, G., et al. (2018). PMB, 63(14), 145006
(**) Fernandez Carmona, P., et al., (2018) Proceedings of PCaPAC2018, FRCC2
slides icon Slides TUB04 [10.992 MB]  
DOI • reference for this paper ※ https://doi.org/10.18429/JACoW-Cyclotrons2019-TUB04  
About • paper received ※ 14 September 2019       paper accepted ※ 26 September 2019       issue date ※ 20 June 2020  
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