An experimental study of focused very high energy electron beams for radiotherapy

Karolina Kokurewicz,Wilfrid Farabolini,Kyrre Ness Sjobak,Davide Gamba,Roberto Corsini,Luca Garolfi,Eugenio Senes,Enrico Brunetti,Dino Anthony Jaroszynski,Alessandro Curcio,Antonio Gilardi

doi:10.1038/s42005-021-00536-0

Abstract

Very high energy electron (VHEE) beams have been proposed as an alternative radiotherapy modality to megavoltage photons; they penetrate deeply without significant scattering in inhomogeneous tissue because of their high relativistic inertia. However, the depth dose distribution of a single, collimated VHEE beam is quasi-uniform, which can lead to healthy tissue being overexposed. This can be largely overcome by focusing the VHEE beam to a small spot. Here, we present experiments to demonstrate focusing as a means of concentrating dose into small volumetric elements inside a target. We find good agreement between measured dose distributions and Monte Carlo simulations. Focused radiation beams could be used to precisely target tumours or hypoxic regions of a tumour, which would enhance the efficacy of radiotherapy. The development of new accelerator technologies may provide future compact systems for delivering these focused beams to tumours, a concept that can also be extended to X-rays and hadrons.

Highlights

Very high energy electron (VHEE) beams have been proposed as an alternative radiotherapy modality to megavoltage photons; they penetrate deeply without significant scattering in inhomogeneous tissue because of their high relativistic inertia
The experiment has been performed at the CERN Linear Electron Accelerator for Research (CLEAR) beamline[40], which is based on an S-band RF accelerator that delivers quasi-mono-energetic electron beams with energies between 60 and 220 MeV
34.65 Gy 11.98 Gy 4.21 Gy 3.8 mm 3.7 mm Conclusion We measured the depth–dose profile of 158 and 201 MeV electron beams focused into a water phantom, demonstrating on-axis dose enhancement at a depth of 5–6 cm, which validates theoretical predictions that focused VHEE beams concentrate dose into a well-defined volume deep in tissue

Summary

Introduction

Very high energy electron (VHEE) beams have been proposed as an alternative radiotherapy modality to megavoltage photons; they penetrate deeply without significant scattering in inhomogeneous tissue because of their high relativistic inertia. 1234567890():,; The main objective of radiotherapy is to kill cancer cells while sparing normal tissue from damage[1] and minimising the creation of secondary cancers This is usually achieved through modalities such as volumetric modulated arc therapy (VMAT)[2], stereotactic radiosurgery (SRS)[3], intra-operative radiation therapy (IORT)[4,5] or brachytherapy.[6] To reduce irradiation of healthy tissue and ensue complete irradiation of tumours[7], dose must be delivered precisely in such a way that it conforms to the tumour shape. VHEEs, in contrast, are very penetrating due to their high inertia, which enables them to reach deep-seated tumours[19,23,24,25,26,27] Their dose is characterised by a sharp transverse penumbra and low scattering at tissue interfaces[14,23,28], compared with current low-energy clinical electrons[29,30]. We present experimental measurements of the depth–dose distribution of VHEE beams focused in a water phantom for several f-numbers and electron energies, and compare these results with theoretical predictions

Methods

Results

Conclusion