Characterization of the Secondary Neutron Radiation at the University Proton Therapy Dresden


Characterization of the Secondary Neutron Radiation at the University Proton Therapy Dresden

Lutz, B.; Zboril, M.; Dommert, M.; Swanson, R.; Enghardt, W.; Fiedler, F.; Reginatto, M.

Radiation therapy is one of the most used treatment modalities of cancer. While most patients receive photon-therapy, a growing number of patients are treated with particles, mainly protons. Protons offers a more localized dose deposition compared to photon-therapy. This allows to reduce the dose that is applied by the primary beam to the healthy tissue outside the target volume. At the same time, the use of protons leads to a change in the composition of the secondary radiation field, when compared to photons. In most locations, the out-of-field dose is dominated by secondary neutrons. The out-of-field dose varies significantly in shape and size. Currently, there is no established procedure to monitor the secondary neutron dose to the patients.
This paper describes the simulation and measurement of the secondary neutron radiation field at the University Dresden Proton Therapy. The simulation uses a detailed model of the beam delivery system, an IBA universal nozzle. The simulations have been validated by a comprehensive set of extended range Bonner sphere spectrometer measurements, with the NEMUS spectrometer operated by the Physikalisch-Technische Bundesanstalt. The set of measurements covers all possible machine configurations for the double scattering mode. An excellent agreement between unfolded measurements and simulation predictions is achieved.
The data shows that the neutron field is varying strongly on the scale of a human body. This indicates that the use of fluence to dose conversion tables is not justified for neutron dose calculation in patients. Therefore, the presented data is of high importance for future studies of the organ doses in different treatment scenarios.

Keywords: neutron; Bonner sphere spectrometer; proton therapy; double scattering

  • Lecture (Conference)
    2018 IEEE Nuclear Science Symposium and Medical Imaging Conference, 10.-17.11.2018, Sydney, Australia
  • Contribution to proceedings
    2018 IEEE Nuclear Science Symposium and Medical Imaging Conference, 10.-17.11.2018, Sydney, Australia
    2018 IEEE Nuclear Science Symposium and Medical Imaging Conference Proceedings (NSS/MIC): IEEE, 978-1-5386-8494-8, 1-6
    DOI: 10.1109/NSSMIC.2018.8824583
    Cited 2 times in Scopus

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Publ.-Id: 27457