NHS High Energy Proton Beam Therapy Centre starts treating patients
Currently, most NHS patients that need high energy proton beam therapy (PBT) have to travel abroad for treatment. However, with the opening of the PBT Centre at The Christie Hospital in Manchester, some patients are now being treated in the UK. A second centre, at University College London Hospital, will ensure that by 2020 treatments can be provided in the UK for all NHS patients needing PBT.
Why Use Proton Beam Therapy?
Proton Beam Therapy is used where tumours are next to sensitive or developing organs, particularly in children, teenagers and young adults, as it provides a more precise method of delivering the radiotherapy dose to the tumour than traditional linear accelerators. This means the chances of the radiotherapy damaging healthy tissues and organs is reduced.
A Radiation Protection Perspective on Proton Beam Therapy
The penetrating power of protons depends on their energy and is selected during the treatment such that all of the protons are absorbed in the tumour. However, when protons are absorbed, they create secondary neutrons with energies up to those of the delivered protons. Shielding must be provided for this neutron field to protect staff working in and adjacent to the PBT facility. Neutron shielding calculations are complex and the associated dose assessment requires information regarding the energy spectrum of the neutrons to be known.
High Energy Radiation Healthcare Facility Design
The radiation shielding for the new PBT centre at The Christie Hospital was designed by specialists at Aurora using Monte Carlo modelling techniques. In order to make the model as accurate as possible, the model geometry included a significant numbers of penetrations (as they can affect the shielding effectiveness), significant items (such as the accelerator) and even gaps between shielding blocks. The secondary neutron field was modelled using information from the equipment supplier, Varian, regarding loss points in the accelerator hall and along the beam line and using clinical workload factors for the treatment room. As this is a new therapy modality in the UK, the design also addressed the uncertainties in the design parameters to ensure the protection afforded by the shielding would be sufficient over the lifetime of the facility.
High Energy Radiation Shielding Integrity Testing
Following the installation of the cyclotron and treatment gantries in 2018, Aurora worked with the The Christie NHS Trust staff and Varian engineers to undertake a comprehensive radiation survey of the new facility. The survey included both neutron and photon radiation measurements, made with specialist equipment both inside and outside of the facility. The survey confirmed that the Trust’s design dose rate constraints had been met.
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