Applications of Accelerators and Detectors to Cancer Treatment

Research group

Research theme

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About

VHEE - Very High Energy Electron Radiotherapy

Very High Energy Electron (VHEE) beams with energies in the range 100–200 MeV are a promising modality for radiotherapy for several reasons. Due to recent advancements in accelerator technology, such as high gradient X-band RF cavities developed as part of the CLIC programme as well as laser-plasma accelerators, it may now be possible to develop a machine more compact and cost-effective than those used for proton beam therapy. VHEE beams are also an attractive choice for the treatment of deep-seated tumours with FLASH-RT, utilising the "FLASH Effect" where healthy tissue sparing is observed when the dose is delivered at ultrahigh dose rates (UHDR) of > 40 Gy/s.  Furthermore, VHEE beams offer several other advantages such as a larger range and sharper penumbra than current clinical electron beams, a lower sensitivity to tissue heterogeneities and the ability to be electromagnetically scanned or focussed.   

The Oxford group is researching the two main technological challenges in the way of translating VHEE-FLASH radiotherapy to the clinic: UHDR dosimetry & beam monitoring and the dose delivery (including uniform beam generation). The group works in close collaboration with the CLEAR Facility at CERN - which is currently in a unique position to be able to provide the beam parameters necessary for pre-clinical and mechanistic studies of VHEE beams at UHDR. 

Ultrahigh Dose Rate Beam Monitoring and Dosimetry

The response of ionisation chambers, which are the gold standard for dosimetry in conventional radiotherapy, becomes non-linear in the UHDR conditions required for the FLASH effect due to saturation effects caused by ion recombination. This effect is even more pronounced for pulsed beams - such as VHEE - since the instantaneous dose is much higher. Therefore new technology is required for both real-time dosimetry and beam monitoring in these conditions. 

The Oxford group, in collaboration with the CERN Beam Instrumentation group, are working on developing a novel fibre array detector for real-time pulse-by-pulse monitoring of the beam profile and dose.

Furthermore, the group is contributing to the development of passive dosimetry protocols which are used for VHEE FLASH studies at the CLEAR facility.

Dose Delivery

An alternative method to magnification optics for providing an enlarged and flattened transverse dose distribution at the patient is a dual-scattering foil. Such systems have been used extensively in the past for hadron and low energy treatment, but few studies have been carried out on the use of dual-scattering foils in the VHEE regime. A number of experiments lead by the Oxford group culminated in the permanent installation of an aluminium and PEEK scattering system in the main beamline of the CLEAR Facility, which can be easily inserted for production of a uniform beam profile at the facility’s in-air test stand and is used for providing uniform beams for VHEE UHDR radiobiological studies at the facility.

Project Collaborators

Past Students

  • Christopher Butler (Oxford, 2019-2023)
  • Thomas Fogg (Oxford, 2020-2024)