Probe: Proton Beam Extension for Imaging and Therapy

Lead Research Organisation: University of Manchester
Department Name: Physics and Astronomy

Abstract

The UK is presently contracting to supply two centres where the NHS will carry out treatment of many cancers with protons. Whilst the current generation of X-ray linacs can deliver excellent treatment using the technique known as intensity-modulated radiotherapy (IMRT), there is nevertheless a small dose inherently deposited in tissues outside of the intended tumour treatment site. For certain hard-to-treat tumours near to critical organs, and in particular when treating some childhood cancers, it would be beneficial to avoid this so-called out-of-field dose. Proton therapy can do this because protons interact in tissue quite differently to X-rays; there is a much more pronounced peak in the delivered dose which can be varied in depth to target the tumour accurately. The two new centres at Christie Hospital and UCLH in London can treat at any depth as they will use high-energy accelerators, augmenting the present low-energy proton centre at Clatterbridge which is restricted to shallow eye treatments.

But there's a problem. Whilst the proton dose is deposited at a specific depth, it can be hard to set the proper energy to reach that depth. This is because current-generation imaging such as X-ray computed tomography doesn't do a good enough job at allowing clinicians to estimate the amount the protons will slow down on their way to the tumour. One promising way around this is to do imaging with protons as well: no conversion from X-ray measurements is needed, but proton imaging needs more energetic protons that can pass right through the patient where their residual energy is measured to work out how much was lost on the way. Suitable high-resolution detectors for this are under development in the UK, but as yet there is no suitable source of the protons themselves.

This is where our linac comes into the story. Recent research at our institute and elsewhere means that we think we can build a linear accelerator (linac) that can boost the protons from the energy available at present adult treatment centres such as Christie up to the energies required for imaging. To retrofit to existing treatment centres requires such a linac to be small, and hence that energy gain must occur in a very short distance; this is the hard part, and requires the use of high-frequency ('X band') accelerating cavities previously developed for use in particle physics experiments. We hope in this project to demonstrate the first truly high-gradient proton linac for imaging, taking the knowledge previously developed for physics research.

Our aim in developing a high-gradient linac is that it can be used to provide improved imaging for patients in the UK and abroad. It is thought that improved imaging using protons could reduce the required margins during tumour treatment by as much as 5mm, sparing surrounding sensitive tissues and thereby reducing side-effects and improving long-term outcomes for patients. Later on, we think the same linac technology could also be used to provide protons directly for treatment, where the use of a linac can allow finer control of the treatment depth. Also, if the accelerating structures can be made small enough, they could even themselves be fitted onto the gantry that rotates the proton beam around the patient, meaning that smaller, cheaper treatment facilities become possible. These single-room centres are seen as one way to increase the access to proton therapy for patients.

We hope our project and the advantages it brings will in the future widen the range of cancers for which proton therapy is beneficial.
 
Description Our key findings are as follows. Firstly, we have demonstrated that a cavity gradient greater than 50 MV/m is feasible - a world's first. We have shown that S-band cavities are more favourable than X-band frequencies when accelerating cyclotron-derived protons for particle therapy; they give a higher gradient and are more economical. We have built a prototype that can deliver the predicted gradients. We have established that high-energy proton tomography is feasible using a linear accelerator to boost the energy of protons from a medical cyclotron.
Exploitation Route Our PROBE prototype cavity demonstrates that high-gradient proton acceleration is feasible, and makes proton treatment based on linear accelerators more viable and likely more economic. A prototype treatment facility is being built by Advanced Oncotherapy at STFC Daresbury Laboratory, and our cavity design could be used to improve the performance of such linacs. Our patents cover all high-gradient cavities of this type, and are applicable across a wide range of technologies outside of particle therapy.
Sectors Healthcare

URL https://epubs.stfc.ac.uk/work/33360751
 
Description Our research has shown that a compact accelerator can provide the 350 MeV protons required for adult patient tomography, particularly when used as an upgrade for existing cyclotron systems. Our design is presently the highest-gradient design for such a purpose. This has encouraged the UK proton therapy community that proton tomography is viable. This was an element of the research case for the Christie Research Beamline, which was successfully funded with over £6M of charitable funding and is now constructed - it is a world-leading, unique facility for the conduct of proton-therapy-related research, and will include research on a variety of topics critical for future patient benefit. These include research on improved methods of patient treatment, radiobiology studies to improve knowledge of what doses are required, and methods to improve imaging. We intend with further funding to test the cavity prototype at Christie Hospital; proton tomography has been identified in the UK and clinical community as a key element in improving patient treatment quality in the future, due to its better potential accuracy than conventional CT and MRI. One particular consequence is that the existing Pravda prototype tomography detector is to be turned into a pre-clinical prototype at the Christie under a new EPSRC grant - OPTIMA. Our PROBE prototype cavity demonstrates that high-gradient proton acceleration is feasible, and makes proton treatment based on linear accelerators more viable and likely more economic. A prototype treatment facility is being built by Advanced Oncotherapy at STFC Daresbury Laboratory, and our cavity design could be used to improve the performance of such linacs. Our patents cover all high-gradient cavities of this type, and are applicable across a wide range of technologies outside of particle therapy.
First Year Of Impact 2017
Sector Healthcare
Impact Types Societal

 
Description OPTIma: Optimising Proton Therapy through Imaging
Amount £3,245,863 (GBP)
Funding ID EP/R023220/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 08/2018 
End 05/2022
 
Description PROBE Collaboration 
Organisation European Organization for Nuclear Research (CERN)
Department CERN - Other
Country Switzerland 
Sector Academic/University 
PI Contribution University of Manchester - specifications, design of beam transport, beam dynamics, provision of research beamline
Collaborator Contribution University of Lancaster - cavity design, PhD student, procurement of cavities, RF testing infrastructure CERN - cavity design, procurement of cavities, RF testing infrastructure, engineering support
Impact 1 cavity prototype 2 patents Disciplines - physics, electrical engineering, mechanical engineering
Start Year 2016
 
Description PROBE Collaboration 
Organisation Lancaster University
Department Department of Engineering
Country United Kingdom 
Sector Academic/University 
PI Contribution University of Manchester - specifications, design of beam transport, beam dynamics, provision of research beamline
Collaborator Contribution University of Lancaster - cavity design, PhD student, procurement of cavities, RF testing infrastructure CERN - cavity design, procurement of cavities, RF testing infrastructure, engineering support
Impact 1 cavity prototype 2 patents Disciplines - physics, electrical engineering, mechanical engineering
Start Year 2016
 
Title PARTICLE THERAPY DELIVERY SYSTEM 
Description A particle therapy delivery system (10) comprising a support structure (12) defining at least a partial enclosure within which a patient is positioned in use, and a particle delivery line for delivering particles to a patient, wherein the support structure (12) is rotatable about a patient, in use, and the particle delivery line comprises at least one linear particle accelerator (14) mounted to the support structure such that particles travelling along the particle delivery line, in use, complete at least one revolution about an axis of the support structure (12). 
IP Reference WO2017212290 
Protection Patent application published
Year Protection Granted 2017
Licensed No
Impact In active discussion with companies with a view to licensing.
 
Title RADIO FREQUENCY CAVITIES 
Description The present invention relates to a device comprising a plurality of side-coupled radio frequency cavities. The device comprises multiple sections, each section having a main axial cavity portion and the sections being stacked in an axial direction such that the main axial cavity portions are axially aligned to form a main axial cavity through the device. A plurality of the sections comprise a partition extending across the main axial cavity such that the partitions are axially spaced along the main axial cavity of the device. The device comprises a side cavity for each partition and an aperture coupling each side cavity to the main axial cavity, each aperture being adjacent its respective partition and interfaces between the sections of the device are aligned through the apertures. 
IP Reference WO2018211282 
Protection Patent granted
Year Protection Granted 2018
Licensed No
Impact In active discussion with companies.