Abstract

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MRI for treatment simulation: Experience in the deployment of a dedicated MRI system and program expansion

There is growing interest in MRI simulation for radiation therapy treatment planning, primarily to exploit the superior soft-tissue contrast available from MRI. The advent of integrated MRI-guided treatment systems is another driver in this area. Many major centres now use this technology, and other centres are soon to follow suit. MRI has been integral to brain radiotherapy for some time, and it is also routine for GU and GYN brachytherapy where available. Approaches for deployment of the service varies greatly from centre to centre, from shared use of diagnostic MRI to dedicated instruments installed in radiation oncology departments.

Our centre recently deployed a new 3 T MRI instrument and expanded program with the opening of a new hospital. MRI simulation was already in routine use at our former site, using a 0.23-tesla open bore electromagnet system. The move to the new site prompted an extensive, ongoing period of training, development, and deployment of new procedures. The presentation will draw from this experience and touch on topics relevant to the deployment of MRI simulation from beginnings to routine operation (see figure). Our objectives are two-fold: 1) to discuss best practices between sites where MRI simulation is already in use, and 2) to inform sites who are projecting the deployment of MRI simulation in the near future.

Installation requires careful planning for purchase and siting of the system, followed by acceptance and commissioning. Design of the facility is an important point. The three major MRI vendors all offer simulation-specific solutions such as wide-bore design, dedicated coils, and customized exam cards. Acceptance of MRI systems can largely be based on AAPM Report 100, with adaptations to modern MRI systems and vendor acceptance procedures. Commissioning tasks should cover the equipment and each of the specific procedures. The input of an MR physicist on staff or in consultation is valuable throughout the pre-deployment process.

Training on the use and safety is primordial to a successful program. Logistics, workflow, and personnel have been the more important challenges at our institution. MRI safety is ingrained in the culture of diagnostic radiology departments, where personnel have been exposed to this technology for decades. On the other hand, radiotherapy personnel (technologists, physicians, nurses, etc.) do not initially possess the knowledge and experience required to work with this technology. Program deployment is an adaptive process. The technical challenges of imaging are most adequately dealt with by a dedicated physicist, preferably one with prior experience in MRI, and with close collaboration with the vendor.

Implementation of a quality assurance program is important to maintaining the highest imaging and procedural quality. Daily system checks are recommended by all manufacturers, while recommendations for imaging tests vary widely. Certain centres perform daily imaging tests, while others rely on weekly or monthly. Radiotherapy-specific issues, such as spatial accuracy, must be considered when developing QA procedures and imaging procedures.

In conclusion, the successful implementation of our MRI-simulation program depended on key steps. These began with planning, installation, acceptance, and commissioning of the system. Clinical deployment, workflow adjustment, staff training on the equipment including safety measures, and rigorous quality assurance of all processes are essential.

Figure 1. Representation of the key steps in the implementation of a dedicated program for MRI simulation in the context of radiation therapy.