B.Lutz: Secondary Neutron Radiation at the University Proton Therapy Dresden

Particle therapy is a strongly growing field in cancer therapy. Approximately 70 treatment centres are currently operating worldwide and the total number will reach more than 100 by the end of 2018(1). The majority of the centres use protons to treat patients like the University Proton Therapy Dresden that started treatment in 2014.

The use of ion beams in radiation therapy allows for the deposition of high doses at the tumour position while minimizing the dose to the surrounding healthy tissue. However, using hadron beams gives rise to a stray field dominated by neutrons. Since the beginning of particle therapy, there is a vivid discussion about the actual size of this secondary neutron field. 

To address this issue, dedicated measurements of the neutron field have been done with an Extended Bonner Sphere Spectrometer at the University Proton Therapy Dresden. Combined with a detailed simulation of the treatment site and beam-delivery system, this constitutes the most comprehensive knowledge on neutron fields during particle therapy world wide.

The talk will give an overview of the passive proton field formation used at the University Proton Therapy Dresden and its modelling in simulation. The working principle of the Extended Bonner Sphere Spectrometer will be explained. The latest status of the analysis of the experimental measurements will be presented.

(1) Particle Therapy Co-Operative Group (PTCOG), www.ptcog.ch