Abstract

Radiotherapy treatment of cancer aims to deliver a lethal dose of X-rays to tumour cells, while limiting the dose to surrounding healthy tissue. A patient’s treatment is planned taking into account organ positions, estimated from a Computed Tomography (CT) scan, then the prescribed dose is administered in between thirty and forty fractions, over a period of about fifty days. Modern treatment machines allow sophisticated shaping of X-ray beams (intensity-modulated radiotherapy), and can perform low-resolution CT scans to help ensure that tumours are precisely targeted (image-guided radiotherapy). A remaining problem is that healthy organs can be at different positions relative to a tumour at each treatment session, both because weight loss may change a patient’s shape, and because many body structures are deformable. This means that the dose received by a volume element (voxel) can be different from the planned dose. Drawing on expertise from oncology, medical physics, engineering and particle physics, the Cambridge-based VoxTox project aims to track actual voxel doses, and to correlate with short- and long-term side effects (toxicity). Results can lead to strategies for modifying dose plans over a course of treatment, bringing clinical benefits in terms of improved outcomes and reduced collateral damage.

This seminar considers radiotherapy treatment from a particle-physics perspective, and summarises the current status of the VoxTox project.