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.

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