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Work by EMPIR project helps to optimise radiation detector for use in MR guided radiotherapy treatments

The project

EMPIR project Traceable dosimetry for small fields in MR-guided radiotherapy (19NRM01, MRgRT-DOS) is developing metrological standards for MR-guided radiotherapy (MRgRT). Over 1.4 million radiotherapy treatments are administered annually in Europe, utilising small beams to deliver optimised doses of radiation to cancerous tumours. MRgRT combines radiotherapy technology with Magnetic Resonance Imaging (MRI) to provide real-time imaging during treatment, allowing for more precise and effective delivery with fewer negative side-effects. The most common form of this kind of therapy is MR-guided X-ray Therapy (MRgXT), though MR-guided Proton Therapy (MRgPT) is also being developed.

The project’s aim is to develop the necessary measurement methodology required to facilitate the use of MRgRT treatments on a larger scale. It is investigating radiation field characteristics and detector properties, as well as generating dosimetrical measurement data for x-ray and proton beams, allowing detectors to be assessed for their suitability. It is also investigating whether measurement methods for MRgXT are applicable to MRgPT, allowing for more rapid uptake of MRgPT.

Project achievements

The project’s work has been used by German dosimetry company PTW, who have begun optimising the design of their ionisation chambers for measurements in the presence of magnetic fields. This optimisation will reduce variation in response between different chambers and will also increase the accuracy of detector response simulations, as small variations in chamber geometry can be difficult to model but can have a big impact on results.

The project has also produced ‘Reference dosimetry in MRI-linacs: evaluation of available protocols and data to establish a Code of Practice’, a review paper on reference dosimetry in the presence of magnetic fields. This will be used in the future by the American Association of Physicists in Medicine (AAPM) and the Dutch commission for radiation dosimetry (NCS) as a basis for producing Codes of Practice for MRgRT reference dosimetry as part of their joint working group.

The achievements of this project are facilitating the development of MRgRT treatments and are a positive step towards more wide-spread uptake of the technology.

Project Coordinator Jacco de Pooter from VSL has said:

“With increasing clinical application of MR guided Radiotherapy it is very important that hospitals have adequate equipment and methods to ensure the quality of treatments. According to our stakeholder committee, currently fields smaller than 2 cm are not used by hospitals in MR guided Radiotherapy because of a lack of proper dosimetric methods and characterised equipment. The MRgRT-DOS project has demonstrated that traceable dosimetry for smaller fields is feasible within the required clinical accuracy of 3 %. With the data measured and the methods developed in the MRg-RT-DOS project the foundation is laid for future CoPs for small field dosimetry in MR guided Radiotherapy which will allow for clinical application of smaller radiation fields.

“In addition, the project has developed experimental facilities which allow for testing detectors under conditions close to clinical MR guided Radiotherapy facilities. Early experiments and simulations on these facilities have led to new information on detector characteristics which will be used by PTW to improve their products. In close collaboration with the stakeholder committee, we ensure that the investigations are tailored to the needs of standards developing organisations, hospitals, and industry. As such, the project is a good example how EURAMET’s ionizing radiation metrology community supports innovation and improves the quality assurance infrastructure in health care.”

This EMPIR project is co-funded by the European Union's Horizon 2020 research and innovation programme and the EMPIR Participating States

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