The power behind new generation radiotherapy
Accelerator science is creating exciting opportunities for research
Although public knowledge of accelerator physics has increased in recent years with the work at CERN on the Large Hadron Collider, many people would not know that they benefit from accelerators in every aspect of their lives. In fact tens of millions of patients receive accelerator-based medical diagnoses and therapy every year.
The most widely known products of medical accelerators are X-rays, which are used for imaging and cancer treatment, and radioactive isotopes, which are used for diagnosis. More recently the use of proton beam therapy has caught the media’s attention as it offers a more targeted treatment for some cancer types, especially for children.
However, despite its value to health and industry, accelerator science is still an emerging area of science and this creates exciting opportunities for research.
Professor Carsten P. Welsch from the University of Liverpool’s Department of Physics, based at the Cockcroft Institute, is coordinating a new pan-European training programme called ‘Optimising Medical Accelerators’. It is due to start this month and will push the frontiers for the use of accelerators in advanced cancer treatment. He says: “There are many questions still to be answered and OMA is positioned at the interface between life sciences, physics and engineering to present an interdisciplinary approach. We have brought together partners from universities, research centres, industry and clinical centres to help define and develop the research programme. The 15 Fellows on the programme will get the opportunity to work with leading research institutes but also to have contact with potential end-users of the technology.”
We have brought together partners from universities, research centres, industry and clinical centres to help define and develop the research programme
The training programme offers a unique approach to research. Involvement by so many key organisations creates a community with an interest in medical accelerators and allows the Fellows to quickly build a network of contacts that will benefit them in their research and future careers.
For example, the Cockcroft Institute is a joint venture between the Universities of Lancaster, Liverpool and Manchester and the Science and Technology Facilities Council (STFC). It is located in a purpose-built building on the Sci-Tech Campus adjacent to the Daresbury Laboratory with its world-class facilities.
Clinical partners are also important, many of which are overseas, but close by is the Clatterbridge Cancer Centre (CCC), one of only a dozen centres in the world to offer ocular proton beam therapy.
Proton Beam Therapy
Protons are positively charged particles created when a hydrogen atom loses its electron. They are formed in an ion source and then can be accelerated, for example in a cyclotron – a compact circular accelerator. Researchers from the Cockcroft Institute have worked closely with Dr. Andrzej Kacperek, Head of National Eye Proton Therapy Centre at the CCC, on a number of projects aimed at optimising the control of the beam.
Unlike most types of radiation used in medicine such as X-rays or electrons, proton beams can be directed to target just the cancer tumour, minimising damage to healthy tissue and leaving zero dose beyond the tumour. This remarkable phenomenon is called the ‘Bragg peak’.
Dr. Kacperek explains: “The degree of precision is unique to proton beams. We can control how deep the beam goes so it can be used to treat a tumour on the iris or one at the back of the eye. Also, as protons scatter very little the beam has sharp edges, which makes it possible to follow the outline of the tumour and protect the optic nerve. We can deliver a very uniform dose by modulating the Bragg peak across the tumour depth.”
However the techniques used for controlling the beam rely on the skill of the operator and sometimes rather basic instrumentation. Although the treatment takes 30 seconds, the equipment calibration and patient set-up can take 20 minutes.
Prof. Welsch comments: “We are working with Dr. Kacperek to automate this process so that more patients can receive treatment – quicker and potentially even at a lower cost. CCC has generously provided us with access to their treatment beamline and allowed us to use it to take measurements. The fact that we can discuss ideas with colleagues that are treating patients on a daily basis is a great advantage; in this way we are always kept up to speed with latest developments and can discuss our ideas with clinical experts.
“For example, we are working with CCC on developing an online beam monitor that will provide clinical operators with full information about the treatment beam during the actual treatment. This will include information about beam position, profile and intensity and hence dose delivered to the patient. If this is coupled to treatment planning software and other imaging diagnostics, then this would provide a much more complete set of information and greater benefit from the treatment.”
Other research themes within OMA focus on improving imaging. There are different types of imaging: initially to determine the size of a tumour; during treatment to follow the beam to ensure it irradiates the relevant areas; and also imaging after treatment. Different techniques are applied at each phase of the treatment cycle.
Additional challenges arise as the internal organs move during treatment when the patient breathes and the beam needs to follow this movement. Prof. Welsch explains that several different techniques are being considered and will be further developed within OMA. For example the German company VIALUX has pioneered some promising camera technologies that are able to determine 3D movement of objects and monitor how a patient’s lung is moving.
We believe that this new approach will provide a truly international and cross-sector training programme that will produce some outstanding young researchers and push the frontiers in this valuable field of science and medicine
OMA also encompasses engineering. The size of medical accelerators means that the building and infrastructures needed to support them are expensive. For example the Heidelberg Ion Therapy Centre features a 670-ton gantry that can be moved around the patient and fills a room the same size as a multi-story building.
There are also other research areas that are linked to the OMA activities and these will benefit from the enhanced simulation, beam handling and diagnostic techniques that the network will develop. For example, there is an international push towards alternative and more compact accelerating techniques, for example high power lasers and plasma fields. Development of a more compact accelerator will make the technology more accessible for smaller clinical centres.
The research team around Prof. Welsch is also involved in these new technologies and is carrying out R&D into very high gradient accelerators to generate high quality beams. These developments are still at an early stage and it will take further studies to fully understand their application potential.
He says that the early career researchers that will be involved in the OMA programme will be working at the forefront of science in a field where there is an international skills shortage: “We are planning numerous outreach events that will also be open to the wider research community and also outreach activities that target schools. We believe that this new approach will provide a truly international and cross-sector training programme that will produce some outstanding young researchers and push the frontiers in this valuable field of science and medicine.”