Secondary Neutron Field at the Dresden Proton Therapy


Secondary Neutron Field at the Dresden Proton Therapy

Lutz, B.; Enghardt, W.; Swanson, R.; Fiedler, F.

Particle therapy is a strongly growing field in cancer therapy. Almost 60 treatment centres are currently operating worldwide and the total number will reach more than 90 by 2017~\cite{PTCOG}. The majority of the centres uses protons to treat patients.

With the increasing importance of particle therapy, the development of application-specific monitoring systems has received a significant boost. On the one side, there are the radio-protection questions like the secondary dose to patients or to radio-sensitive equipment. On the other side, there are the methods that intend to verify the correct application of the treatment dose, during or short after the treatment, like prompt-gamma-imaging or -timing, or PET. For both groups of measurements, a good understanding of the secondary radiation field is crucial.

The greatest challenge in determining the secondary radiation field comes from neutrons. The spectra of the neutrons, generated by protons of therapeutic energies, extend far beyond the specification of most commercially available dosimeters. Additionally, the generated neutron fields are spatially nonuniform and in case of passive field formation strongly dependent on the operational setting. Combined with the very limited spatial and spectral resolution of the available neutron detectors, many details of the field cannot be experimentally resolved. Therefore, a dependable measurement of the neutron field requires a detailed simulation of the neutron generation in the treatment system.

The OncoRay treatment centre at the University Hospital Carl Gustav Carus operates an IBA universal nozzle that is capable of providing both scattered and scanned proton beams. This nozzle has been modelled in detail by means of the TOPAS software~\cite{TOPAS}. TOPAS provides a text-file based interface to Geant4~\cite{Geant4} Simulation Toolkit with focus on proton therapy applications.

The talk gives an overview of the specific implementation of the IBA nozzle. It presents the predicted secondary neutron fields and discusses how these depend on the operational parameters of the nozzle. Finally the results are compared to experimental measurements.

  • Lecture (Conference)
    1st Workshop Helmholtz Cross Program Activity - Querschnittsthema Strahlenforschung “Sekundäre Neutronen in Medizin und Strahlenschutz”, 24.-26.11.2015, München, Deutschland

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Publ.-Id: 22886