The following partners contribute to the project as part of the consortium:

As the national metrology institute of the Netherlands, VSL develops and maintains primary dosimetry standards and measurement techniques for existing and advanced radiotherapy applications. Moreover, VSL has ample experience in applying primary standards on-site in clinical facilities. Based on these capabilities, VSL makes measurements in hospitals, companies and other laboratories directly traceable to international standards. This is done by research projects, the development of new measurement set-ups, measurement services (such as calibrations), participation in the development of dosimetry protocols used by medical physicists and training courses.

Dr. Jacco de Pooter, project coordinator of the MRgRT project: “MR guided radiotherapy (MRgRT) requires considerable advancements in primary standardisation and the development of dosimetry protocols. The focus of research at VSL is on advanced radiotherapy modalities and VSL has already developed considerable experience in previous EMRP projects. Therefore, being part of the Metrology for MRgRT project as a coordinator is a logical choice.”

“MRgRT is one of the two major developments in today’s radiotherapy (the other being proton therapy). It will lead to patient treatment in which real-time image information will guide the dose optimisation and delivery. This is not possible with current radiotherapy modalities, leading to unnecessarily large safety margins around target volumes.”

VSL will be responsible for the application of the recently developed water calorimeter in MRgRT facilities (Work Package 1). This calorimeter essential will allow correction factors to be measured for application in reference dosimetry protocols. In addition, VSL will deploy its expertise in Monte Carlo simulations in the presence of magnetic fields to develop benchmark tests for Monte Carlo simulations (Work Packages 2 and 3).

www.vsl.nl

The Physikalisch-Technische Bundesanstalt (PTB), Germany’s national metrology institute, is a scientific and technical higher federal authority falling under the competence of the Federal Ministry for Economic Affairs and Energy. PTB consists of 9 scientific-technical divisions, including Ionising Radiation.

Dr. Ralf-Peter Kapsch, head of the high-energy photon and electron radiation working group at PTB: “It is expected that an increasing number of MRgRT facilities will be installed in Germany over the next few years offering new possibilities for cancer treatment. This will also lead to new challenges for medical physicists responsible for the quality assurance and the correct irradiation of patients. PTB is amenable to law for the unity of measurements in medicine (in Germany) and for the promotion of the international harmonisation of metrology. For these reasons PTB is very interested in the development of an internationally harmonised guideline for medical physicists, a Code of Practice, applicable in MRgRT, which is one of the main goals of this project.”

“Based on the increasing precision in application, radiotherapy relies more and more on accurate imaging of the patient and the tumour to increase the cure rate. This also implies that the existing high spatial dose conformity with the tumour needs to be adaptable to temporal changes. Image guided, and especially MR guided radiotherapy allows the next big developmental step forward in reaching this aim.”

PTB contributes to the MRgRT project by:

  • investigating the behaviour of dosimetric detectors in magnetic fields, both experimentally and by Monte-Carlo simulations (Work Package 1 and 2)
  • providing experimentally determined correction factors and other input data needed for the development of a Code of Practice (Work Package 1)
  • validating Monte-Carlo codes with experiments (Work Package 3)
    developing independent motion surrogates based on ultra-wideband radar for internal organ movement tracking (Work Package 4)
    “The biggest challenge will be to implement a metrological framework which allows traceable measurements of absorbed dose to water in MR guided radiotherapy in clinics.”

www.ptb.de

The National Physical Laboratory (NPL) is the national measurements institute of the UK. It maintains the national measurement standards, including the radiation dosimetry standards.

Dr. Simon Duane, Principal Research Scientist of NPL: “MR guided radiotherapy (MRgRT), an advanced technology for cancer treatment, combines a linear accelerator (linac) with a Magnetic Resonance Imaging (MRI) scanner. The combination of these two machines is important because allows real-time tumour visualization during treatment, in contrast to current X-ray imaging techniques.  This provides high accuracy of soft tissue localization of either the tumour or the organs at risk, while completely avoiding the radiation dose associated with X-ray CT. MRgRT will change the way that the patients have been treated so far. It will potentially improve real-time adaptive planning based on high contrast moving visual images of the change of the tumour characteristics.”

The main contribution of NPL to this project is to develop methodologies for testing Monte Carlo based radiation transport algorithms for accurate beam modeling and detector response simulations in external magnetic fields (Work Package 3). NPL will also contribute to the development of primary and secondary standards for traceable dosimetry under reference conditions for MR guided radiotherapy (Work Package 1) and methodologies for accurate measurements of TPS data as well as for machine QA measurements (Work Package 2).

“The biggest challenge for NPL is the benchmarking, for both internal consistency and experimentally, of several general purpose codes in realistic conditions for simulation of radiation transport in the presence of magnetic fields. Since the underlying physical mechanisms are not well understood, traceability for radiation dosimetry and adequate knowledge of detector characteristics is also a main challenge.”

www.npl.co.uk

CEA is the French atomic energy commission. Its laboratory LNHB (Laboratoire National Henri Becquerel) is the French national metrology laboratory for ionising radiation designated by LNE. The fields covered by CEA-LNHB are radionuclide metrology and the dosimetry of photons and charged particles. In those fields, the laboratory develops and maintains references, and transfers them to accredited standard laboratories and to end users.

Dr. Christel Stien of LNHB: “In the past few years, we have been working on gel dosimetry. Since the response of the gel should not be influenced by the magnetic field and as its reading method is actually MRI, it is a good candidate MR-guided radiotherapy (MRgRT) dosimetry. This project offers us the opportunity to work together with other European NMIs and also with clinical institutes that are aware of treatment conditions and all of the constraints and that can go with them.”

“Even though the installation of these facilities is not planned yet in France, MRgRT is certainly an emerging treatment technique for the coming years and we want to develop knowledge on the technique. The permanent magnetic field inherent to MR measurements must have an impact on most of the punctual, 2D and 3D dosimeters measurements. This has to be investigated and tools have to be developed in order to take into account those new modalities.”

CEA-LNHB will use gel dosimetry for measurements aimed at the quality control of the machine and also in anthropomorphic phantoms (Work Packages 2 and 4). “To make it suitable for the intended measurements, the dosimetric properties of the gel have to be improved, particularly in terms of uncertainties and dose threshold.”

www.list.cea.fr

The Federal Institute of Metrology (METAS) serves as the Swiss centre of competence for all issues related to measurement and for measuring equipment and measuring procedures in Switzerland. It develops the national measurement base, that is to say it looks after the physical implementation, mutual comparison and thus the international recognition of measurement units.

Dr. Christian Kottler, head of laboratory at METAS: “MR guided radiotherapy (MRgRT) is an innovative topic. Even though this technique is not yet applied in Switzerland, radiotherapy centres are still growing and MRgRT may become relevant in Switzerland in the coming years. In that case, there will be a need (and also an obligation) for METAS to provide respective knowledge and calibration services. We are happy to join this project to be at the forefront of these developments.”

“METAS has been active in the field of accelerator dosimetry for several decades. METAS will contribute to the project for the comparison of dosimetry methods (Work Packages 1 and 2). METAS works with Fricke dosimetry measurements, a chemical dosimetry method which is expected to show little perturbation in a magnetic field. In Fricke dosimetry the handling of chemical solutions in synthesis as well as in the application is crucial because it enables the stability that is required in the dosimetric application. For instance, undesired oxidation caused by impurities will alter the dose measurement reading if it occurs between the irradiation and the optical readout reading. Since measurements will be performed at the partner’s facilities, methods and procedures have to be developed that enable preparation, handling and readout for Fricke dosimetry measurements on-site.”

www.metas.ch

The Cancer Sciences Division of the University of Manchester and The Christie, expert institute in cancer care, research and education, joined forces by participating in this MRgRT project. The Radiotherapy Physics group of the University of Manchester focuses on accuracy of radiotherapy including target volume definition, treatment planning, image guidance and treatment follow-up. It is part of the radiotherapy related research group and works closely with the proton research team, physicians and biologists united in this group. The team is located at The Christie and collaborates on a daily basis with physicians, physicists and engineers in the clinical radiotherapy department, which hosts an MR-linac system.

Prof. Dr. Marcel van Herk, Professor of Radiotherapy Physics, is happy to participate in this EMPIR project: “MR guidance promises to be a next important step in improving the accuracy of radiotherapy. Higher accuracy means that radiation can be more focused on the disease, allowing higher cure rates and/or less toxicity. However, MR guidance also brings problems. The calibration of the machine, with its high magnetic field, is difficult since most measurement devices are affected by it.”

“We are looking forward to collaborating with some partners that we already know, and with partners that are new to us. Collaboration allows joint development of solutions. An important aspect of the project is that the potentially higher geometric accuracy also means that particular uncertainties in the treatment process are now becoming the weakest link. I tend to focus on tumour definition uncertainty – doctors do not fully agree on where tumour boundaries are located.”

“Our aim is to develop simulation software that evaluates the effect of dosimetrical and geometrical uncertainties on outcome (Work Package 4). This allow physicists and doctors to play ‘what if’ scenarios and avoid the risk of irradiations being too small due to part of the uncertainties having been ignored when calculating appropriate treatment margins.”

“Our biggest challenge will be to make the simulation software easy to use and safe, using realistic estimates of all the uncertainties.”

www.research.manchester.ac.uk

www.christie.nhs.uk

The Department of Radiotherapy is part of the main research line Personalized Cancer Care of the UMC Utrecht Center for Image Sciences. The main research line of the department is MRI guided radiotherapy.

Prof. Dr. Bas Raaymakers, Professor Experimental Clinical Physics at the Department of Radiotherapy of UMC Utrecht: “In a longstanding, joint effort with Elekta and Philips, UMC Utrecht has designed and developed the hybrid MRI radiotherapy system. Currently we have two prototypes installed for technical research and a third system is being prepared for clinical introduction. We foresee much improved radiotherapy by offering MR imaging to the radiation oncologist during the radiation delivery.”

“The anatomical feedback from the MRI can be used to reconstruct exactly what has been done during the treatment. This knowledge can be used to optimise the remaining treatment fractions. Moreover, MRI enables live feedback for motion compensated radiation delivery and the possibility to work towards real-time plan adaptation. Together, this should lead to a more precise radiation delivery of moving tumours, implying better cure with less toxicity.”

“This project is a very good showcase of the joint efforts needed to bring dosimetry for a new system like this to the clinic. Additionally, it enables the development of new technology that might also be used in existing clinics.”

“In this project we will contribute in all work packages, making use of the experience we have gained from developing the system, ranging from reference dosimetry and machine dosimetry to patient dosimetry and design of procedures for on-line QA. Also because of the presence of multiple MRI linacs systems, we provide a test site for the development, evaluation and implementation of the techniques in this project.”

www.umcutrecht.nl

Within the German Cancer Consortium (DKFZ), cancer researchers and medical practitioners collaborate closely to speed up the transfer of new diagnostic and treatment approaches to clinical practice.

Prof. Dr. Christian Karger, group leader of the Research Group Applied Medical Radiation Physics: “Our department has longstanding experience with modern treatment concepts such as conformal radiosurgery, 3D radiotherapy, IMRT as well as proton and ion beam radiotherapy. Our focus lies on optimising treatment techniques and developing methods to facilitate and validate complex treatment techniques. Besides conventional linear accelerators, Tomotherapy and Cyberknife devices, Heidelberg will be one of the first sites in Germany to receive an MR-integrated linac device. This device poses several challenges, which are addressed by this project.”

“MRgRT is important because it allows the alignment of tumours and normal tissues to be assessed directly fraction by fraction before treatment with superior soft-tissue contrast (interfractional motion). Real-time motion monitoring of tumour and organ motion (intrafractional motion) will make treatment more accurate and functional information can be included in radiotherapy treatments. The information gained from this project may be used as a basis for the development of adaptive treatment concepts.”

In this project, DKFZ will contribute to the development of general, patient-specific and workflow QA and end-to-end testing for the clinical application of MRgRT (Work Package 4). “One of the biggest challenges will be to simulate the complete treatment chain in realistic conditions, i.e. in the presence of inter- or intrafractional motion, and to efficiently measure the dose distribution in 2D or 3D.”

www.dkfz.de