Particle accelerators have been used for medicine since the earliest days after their invention, and already in 1896 Herbert Jackson realised that the greater energies and superior directionality afforded by accelerated particles could be advantageous over decay radiation for the treatment of cancer. Since then the field of accelerator-based radiotherapy has blossomed, and today the majority of radiotherapy is carried out using x-rays derived from small (c.10s of MeV) electron linacs; the UK for example has over 180 of them.
Protons and heavier ion species benefit from the finite range afforded by the Bragg peak that occurs when they slow in matter, and although this idea was first tried at Berkeley in 1952, it was only in 1989 that the first hospital-based centre in the world at Clatterbridge started treating patients with protons. Whilst Clatterbridge led other hospitals in providing protons, it is limited to rather shallow treatments of the eye by its 62 MeV proton energy.
Artist’s impression of the building to house theProton Beam Therapy centre at Christie Hospital.
In the intervening years there has been a growing case for the treatment in the UK of other cancer types with protons, including early exploratory case studies for laboratory-based therapy at both the Daresbury and Rutherford national laboratories. Following a Department of Health programme to develop proton therapy treatments within the UK, all this work has recently culminated in the selection of Varian Medical Systems to install two 3-room proton therapy systems at the Christie Hospital in Manchester and at UCL Hospital in London. Technical advice on the required specification of these systems was provided by members of the Cockcroft Institute and UCL, as well as by overseas physics laboratories such as the Paul Scherrer Institute. These centres will eventually each treat 750 patients per year after treatment commences some time in 2018 – augmenting the existing referral of patients to centres overseas – and is likely that construction will commence in the next couple of months. At one centre (Christie) there is planned to be a research beamline providing protons at energies up to nearly 250 MeV, which may be used for such research purposes as accelerator component development, diagnostic instrumentation, and radiobiology.
It is therefore an exciting time for the use of accelerators in medicine in the UK, and the research opportunities afforded to accelerator scientists in this area have led to a resurgence of interest in helping improve such technology at national labs, institutes and universities. One notable example in the UK was the recent culmination of the EMMA and PAMELA programmes. As probably most PAB members know, the EMMA project successfully demonstrated the non-scaling FFAG principle in a test accelerator; as well as guiding technology choices for future neutrino and muon facilities (for example in recent work on nuSTORM), EMMA also gave confidence that FFAGs might be used for particle therapy. The PAMELA design study showed an innovative design for both proton and carbon therapy that might improve treatment by delivering dose at different energies more rapidly; moreover, it was truly a UK-wide and world-wide accelerator collaboration involving researchers at many centres, supported by the excellent engineering implementation at Daresbury Laboratory. The NORMA FFAG design has followed on from this activity to pursue a proton-only facility but at higher energy.
Today there are many UK groups interested in developing future accelerators to be used in medicine, not only for particle therapy but also for the other key application – the production of radioisotopes for medicine. Several approaches have been proposed for both applications, and in the UK three main areas of interest are currently apparent: the use of high-gradient or high-current conventional RFQs and/or linacs; the use of FFAGs; the use of laser-based methods to accelerate protons. One important motivation has been the burgeoning crisis in the supply of technetium-99m – the isotope used in 85% of global nuclear medicine procedures – and a number of accelerator projects have sought to address it. The most likely method that could be commercially viable is to use high-current proton cyclotrons to irradiate enriched molybdenum targets, as recently well demonstrated at TRIUMF and University of Alberta; a recent UK review of technetium provision by the NHS and British Nuclear Medicine Society has endorsed this view (http://arxiv.org/abs/1501.03071). However, alternative methods using electron linacs or laser-based acceleration are also in development as are plans to produce technetium with FFAGs, and for example test irradiations of targets were carried out in 2013 at RAL’s Vulcan laser to produce technetium using proton bombardment. The IAEA has also recently completed a research programme of work on accelerator-based methods for technetium production.
STFC have recognised the research potential of medical accelerators in several recent calls to their Futures and other programmes. In particular there is a planned UK-wide network on advanced radiotherapy (led by Karen Kirkby) to better bring together clinicians and technologies to improve radiotherapy; organised under the auspices of the national CTRad radiotherapy research working group, this network has followed several of their meetings to define clinical needs for future UK developments in this area. In the coming months the network will also bring together the UK groups working on accelerator technology to help define the research programme in these topics. Funding will be available through this network to train researchers, provide seed funding, and exchange research knowledge.
Another important activity the UK is involved with is the EUCARD2 programme, and in particular Work Package 4 (led by Rob Edgecock) which addresses accelerator applications through networking activities. Several high-profile workshops have already been held, and the UK has hosted (at Cockcroft Institute) workshops both on particle therapy gantries in 2014 (https://indico.hep.manchester.ac.uk/conferenceDisplay.py?confId=4226) and on compact accelerators for medical isotopes in 2015 (https://indico.cern.ch/event/366464/). Both workshops had very good attendance not only from European research groups and those further afield, but also commercial companies were well-represented. Other workshops have included ones on neutron production and for boron neutron capture therapy for which there is also UK clinical interest. These workshops have already spurred greater collaboration amongst European researchers, and it is planned to augment this networking activity in the follow-up to EUCARD2.
EUCARD2 WP4 has also recently launched the development of a European-wide report on the applications of particle accelerators in Europe – APAE. Planned to be published in early 2017 and to be endorsed by European research labs, this report will form a consensus of the future priority directions for research to improve the use of accelerators in several key areas: energy, health, industry, security, photonics, and neutrons. Chaired by Angeles Faus-Golfes, the contributions to two chapters (health and security) will be coordinated by UK accelerator researchers, and this report is an opportunity for groups to help define the research that could be funded in future national and European programmes. The kick-off meeting was held on 18/19 June at the prestigious Royal Academy of Engineering in London (http://indico.cern.ch/event/377384/) with about a hundred people attending. The next steps are to solicit contributors to the report chapters; interested researchers in the UK are encouraged to get involved.
Author:
Hywel Owen, (Accelerator Physics Group University of Manchester/Cockcroft Institute) (hywel.owen@manchester.ac.uk)