Proton Beam Therapy Dose Calculations and Evaluation using MRI

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1) Brief description of the context of the research including potential impactThe Proton Beam Therapy (PBT) centre at UCLH has started treating patients. PBT is a precise radiation treatment in which a highly concentrated dose can be delivered to the target. Compared to photon-based radiotherapy (RT), PBT patients should benefit from reduced dose to surrounding healthy tissue; this makes PBT a favourable treatment option for tumours in particularly radiosensitive regions, however, accurate and reliable treatment planning is critical for realising the benefits of PBT.There is clear potential for MRI to be further utilised in PBT. Follow up MRI scans present an opportunity to retrospectively evaluate PBT treatment through radiation associated image changes (RAICs). Retrospective treatment evaluation is especially useful for PBT since the true position of concentrated dose can't be verified during treatment. Characterising RAICs in PBT would enable retrospective evaluation of treatment accuracy and would facilitate investigations into the susceptibility and response of specific structures to radiation dose. CT is used for treatment planning and dose calculation since proton stopping power is strongly influenced by electron density. CT is also more efficient and offers better geometric accuracy than MRI, however, CT scans impart considerable radiation dose to healthy tissue so carry greater patient risk. MRI-only treatment planning for PBT has been proposed to reduce dose from CT to healthy tissues in radiosensitive regions. For PBT, this technique would utilise the tissue classification potential of MRI to produce more informed maps of proton stopping power. The feasibility of both MRI use cases PBT is limited by the variability of intensity and image contrast obtained through conventional MRI. To realize MRI-only treatment planning and evaluation, quantitative MRI techniques will need to be refined and optimised.2) Aims and ObjectivesThere is clear potential for the benefits of MRI to be further utilised in PBT. This project aims to develop the MRI scans acquired throughout PBT treatment to improve treatment planning and evaluation. Initially, this project will focus on paediatric brain cancer treatments; the brain is relatively motion-free and there is extensive available software from the neuroimaging community for image registration, segmentation, and correction. The specific objectives are to:- Investigate image processing techniques and develop quantitative MRI sequences to enhance visibility of RAICs- Review physical models of proton stopping power to understand the influence of different tissue properties on dose distribution.- Relate observations through follow-up MRI scans to practical improvements in PBT treatment planning.- Evaluate feasibility and practical utility of MRI-only treatment planning for clinicians and patients. Refine MRI sequences and existing techniques for generating maps of proton stopping power.3) Novelty of Research MethodologyIn this project, novel MRI sequences will be developed for PBT treatment planning and evaluation. Previous studies have performed preliminary investigations into treatment planning and evaluation using MRI, however these studies have been based on conventional MRI sequences which are not designed for these purposes. This project will explore and refine quantitative MRI sequences to optimise their capacity for PBT treatment planning and evaluation.4) Alignment to EPSRC's strategies and research areasThis project is aligned with EPSRC's 'Medical imaging - including medical image and vision computing' research area. 5) Any companies or collaborators involvedThis project is in collaboration with the NHS Proton Beam Therapy service at University College London Hospitals NHS Foundation Trust.