High-energy proton beam therapy offers potential treatment option for eye cancer

Particle beams - from low energy beams with exotic ions through to extremely high energy light sources - are revolutionising the way we view the world and creating potential for new industries, but the instrumentation for controlling the beams is still in its infancy.  An international project, coordinated by the Cockcroft Institute, Liverpool, is fast tracking development of vital tools that will allow us to control the power of the beam. 

One promising application is proton therapy.  The Clatterbridge Cancer Centre NHS Foundation Trust is one of only dozen centres in the world to offer ocular Proton Beam Therapy. A partnership with the Cockcroft Institute promises to optimise control of the proton beam, significantly shortening treatment time and creating a leading position for the UK in this emerging field of technology. 

Prof. Carsten Welsch, Associate Director, of the Cockcroft Institute explains, "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 is particularly important in the eye. However the techniques used for controlling the beam rely on the skill of the operator and sometimes rather basic instrumentation. We are working to automate this process to shorten the treatment time." 

Protons are positively charged particles, created when a hydrogen atom loses its electron. They are formed in an ion source and then accelerated, for example, in a cyclotron - a compact circular accelerator. 

Dr Andrzej Kacperek, Head of Cyclotron at The Clatterbridge Cancer Centre explains that when the Douglas Cyclotron commenced proton therapy 24 years ago it was one of the few in the world to offer this type of ocular therapy. Thus the team here had to make much of its own instrumention which was challenging but successful. In fact some of this equipment has been used at other newer centres. 

Dr Kacperek says, "Protons are heavy charged particles that penetrate tissue for a short precise distance and deposit most of their energy at the end of the beam so the target cancer is destroyed but the healthy tissue is spared. This remarkable phenomenon is called the 'Bragg Peak'.  

"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 consistent dose by modulating the Bragg peak across the tumour depth." 

Dr Kacperek has a 'Bragg Peak Wheel' (made from Perspex), to help measure the modulation and proton range required. A brass collimator is made at the workshop for each patient that tailors the cross-section of the beam to the exact shape of the tumour.  He is delighted by the support he is getting from researcher Tomasz Cybulski of the Cockcroft Institute to automate these procedures, made possible via the European Commission funded DITANET Project. 

Tomasz Cybulski says the beam intensity determines the extent of the damage to the malicious cancer cells so measuring the current is vital to determining the dose given to the patient. 

 "We are looking at non-invasive ways to measure the beam to provide quality assurance. For this we are looking at the beam halo, which is created by natural scattering of protons when the beam passes through the air to reach the patient's eye.  The mechanical design for this detector has been finalised and we are now working on the electronics.

"The beauty of working with the team at Clatterbridge is the expertise they have in running the Cyclotron.  This knowledge has been invaluable." 

Dr Kacperek says, "The treatment takes only 30 seconds but the session takes 35 minutes as you need to manually calibrate the equipment as well as positioning the patient.  If we can reduce this time we could see more patients in peak periods or reduce the runtime for the Cyclotron in slack times which would be a massive cost-saving." 

Improved instrumentation for proton therapy is one of the many outcomes of the DITANET Project, coordinated by the University of Liverpool from the Cockcroft Institute, which aims to develop beam instrumentation. 

Although public knowledge of accelerator physics has increased in recent years with the work at CERN on the Hadron Collider, it is not yet a 'classic' area of physics and the techniques for controlling the power of the beam are still at an early stage.

The DITANET Project aims to address this gap and fast track development of essential tools by creating a community of researchers across industry and academia. Before coming to the Cockcroft Institute, Prof. Welsch's research career led him to Japan, the USA, Germany and Switzerland. During this time he saw clearly the need for greater collaboration, in particular with industry. 

"Detailed diagnostics of charged particle beams is still an emerging area with many opportunities for ground-breaking research and a growing range of industrial and medical applications. There is a strong need for many more researchers trained in this interdisciplinary area. To define an ideal and comprehensive training program, we have got business, universities and research centres involved at an early stage of the DITANET project to define their individual requirements and provide placements for our researchers."  

Instrumentation that will improve proton beam therapy has huge commercial potential, Analysts CSIntell estimates that in 2011 the global proton therapy device market reached US$350 million and predicts it to be growing at 9 per cent.  

The NHS is investing £250 million in two new high-energy proton beam therapy units at Christie NHS Foundation Trust in Manchester, University College London Hospital and University Hospitals Birmingham NHS Foundation Trust. The work developed at Cockcroft by the DITANET project has the potential to reduce running costs and increase patient throughput at these new facilities.