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New standards to enable safe, effective treatment of cancer with emerging MR-guided radiotherapy

The project
Cancer, the leading cause of death in Europe after cardiovascular disease, is responsible for roughly one in five deaths. Radiotherapy, which uses beams of ionising radiation to kill cancerous cells, is one of our most important defences against cancer and is used to treat around half of patients in Europe.

Magnetic resonance (MR) guided radiotherapy is a recently developed cancer treatment being considered by cancer treatment centres worldwide. By combining the soft-tissue imagining capabilities of magnetic resonance imaging (MRI) and high-energy radiation treatment, the technology offers the potential for faster diagnosis and treatment turnaround. The real-time imaging of patient anatomy during radiation treatment sessions allows clinicians to accurately target cancer cells.

However, when active at the same time radiation beams and magnetic imaging fields can interfere with each other, effectively making existing radiation dosimetry calibration methods redundant. So, before prototype MR guided radiotherapy devices could be approved for patient use, new trusted methods were essential to support their use in practice.

Completed EMPIR project Metrology for MR guided radiotherapy (15HLT08, MRgRT) has developed new standards and measurement methods, adapted for MR-guided radiotherapy, to enable medical physicists to develop safe, accurate treatment plans. This metrological framework supports the clinical implementation of MR-guided radiotherapy, accelerating the rollout of this state-of-the-art treatment.

Case studies

Two case studies describe how this project enabled the delivery of accurate radiation doses to patients:

• Absolute dosimetry for MR-Linacs describes how this project supported CE mark approval for a Magnetic Resonance Linear Accelerator (MR Linac), clearing the device for commercial sales and clinical use across Europe. Regulatory clearance thereafter extended to 35 countries.
• Trusted MR-guided radiotherapy planning describes how the project provided reliable absolute dosimetry that could be practical for routine treatment. Later the first clinical treatment of a patient with long term prostate cancer was announced, allowing for adaption of treatments as treatment progressed, reducing the time to create the treatment plan from days to a few minutes.

Project Coordinator Jacco de Pooter from VSL said

‘The MRgRT project has paved the way for accurate radiation dosimetry in presence of magnetic fields, as needed for MRI linacs. Many of its findings are now being used by working groups developing documentary standards for dosimetry in MR-linacs. Given the worldwide increase in MR-guided radiotherapy the development of these standards is extremely important.'

This work is continuing in the follow-on project Traceable dosimetry for small fields in MR-guided radiotherapy (19NRM01, MRgRT-DOS).

These EMPIR projects are co-funded by the European Union's Horizon 2020 research and innovation programme and the EMPIR Participating States.

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