The Elekta Unity MR-Linac is in the vanguard of a new generation of MR-guided radiotherapy (MR/RT) systems that enable clinicians to visualize a tumour target, as well as its surrounding anatomy, with exceptional soft-tissue contrast both prior to and during treatment. Those capabilities are now poised to transform workflows in the radiation oncology clinic, delivering resource efficiencies and improving patient outcomes in the process.

It’s a compelling picture, one in which MR/RT points the way to personalized medicine tailored to the unique requirements of each patient – adjusting radiation delivery to address the daily variation in the tumour and surrounding healthy tissue, while enabling the clinician to adapt the plan for tumours that respond rapidly to treatment, as well as those that prove unresponsive to standard doses of radiation. Furthermore, that ability to capture the tumour and its environment “on the fly” will, in turn, make it possible to increase the radiation dose to diseased tissue in real-time without damaging adjacent organs at risk and other critical structures.

Among the early-adopting clinical customers for Elekta Unity is the US-based Allegheny Health Network (AHN), which is currently putting the finishing touches to a new $100 million academic cancer centre at Allegheny General Hospital (AGH) in Pittsburgh, Pennsylvania. This integrated cancer clinic will begin patient treatments later this summer using an array of cutting-edge radiotherapy systems, including the Elekta Unity MR-Linac and two additional Elekta machines (an Elekta Versa HD with onboard imaging and robotic table; also a Leksell Gamma Knife Icon with cone-beam CT and motion management).

Work in progress

Right now, the MR-Linac is still under construction at AGH, with the Covid disruption forcing the launch schedule back a couple of months. “Hopefully we’ll be moving into commissioning for the Unity over the next few weeks and are pushing for initial patient treatments in late September or early October,” explains Tom Colonias, a radiation oncologist at AGH and clinical lead on the hospital’s Elekta Unity project.

In the meantime, there’s a comprehensive training and applications programme in place so that Colonias and his colleagues are ready, from day one, to exploit Unity to the full. A case in point is the system’s on-board MR imaging capability. “We use MR scans all the time in radiation oncology,” says Colonias, “but we don’t perform the scans – they’re done in radiology. As a result, the whole department has to be MR-trained regarding the health and safety aspects of working in a magnetic-field environment.” To provide a focal point for that expertise, AGH is putting three of its radiation therapists through MR certification so that they can run the MR scanner on a day-to-day basis (although such certification is not mandatory for Unity).

Elekta’s engineering and physics teams are also working closely with AGH medical physicists to implement a rigorous and standardized approach to system acceptance, commissioning and quality assurance (QA). “We’ll be using specialized MR-safe phantoms for the commissioning QA,” says Colonias, “as well as recruiting volunteers so that we can verify the performance of the MR scanner on real people.” What’s more, all of the QA techniques and equipment for the Unity are developed to be MR-safe – from end-to-end workflow tests utilizing both the linac and MRI components of the system to patient-specific QA for each adapted plan of treatment.

In the run-up to the Unity system going live, AGH’s multidisciplinary clinical team will make recommendations on initial patient selection. On a practical level, it’s likely they will kick things off with prostate treatments and pelvic malignancies (as in each case there’s no significant organ motion and there are plenty of patients available). “It’s going to be a learning curve at the outset, getting the Unity workflow defined and really efficient,” explains Colonias. “Within six months of being operational, though, we aim to be doing real-time adaptive planning and treating up to 10 patients a day.”

Longer term, the adaptive capabilities of Unity will enable AGH to address the inherent complexities of a wide range of disease indications (see “The AHN roadmap for MR/RT”, below). Between treatment sessions, for example, patients can gain or lose weight; their stomach, bladder and bowel contents change; their organs may shift, rotate or deform; and their tumours may shrink, move or rotate. With this in mind, AGH clinicians are already planning MR-Linac studies of liver stereotactic body radiotherapy (SBRT) and pancreas SBRT, alongside a specific interest in exploring stereotactic ablative radiotherapy (SABR) to treat ventricular tachycardia (a potentially fatal condition in which the heart beats at more than 100 beats/min).

Another priority is head-and-neck cancer. “Owing to potential weight loss and tumour response during therapy, head-and-neck cancer patients can be ideal candidates for the adaptive planning afforded by the Unity,” notes Colonias. “Such adaptive treatments may result in better functional outcomes and improved quality-of-life post-treatment.”

Collaborate and accumulate

More broadly, membership of Elekta’s MR-Linac Consortium has been fundamental to the MR/RT learning experience for Colonias and his colleagues. One aspect of the Consortium is a knowledge-transfer programme that brings together more than 35 clinical institutions – all of them Elekta Unity customers – as part of a collective conversation focused on driving improved patient outcomes through the application of MR-Linac technology.

AHN has been involved with the Consortium for a couple of years, taking advantage of the regular international meetings to fast-track the training of its radiation oncology team on all aspects of Unity best practice – from treatment planning and MR safety to QA protocols and online adaptive workflows. “We’re starting out-of-the-box here at AHN with a new way to treat patients,” says Colonias. “As such, the Consortium is a great vehicle for us to talk, collaborate and learn along the way with other clinical institutions.”

What’s notable, Colonias adds, is that the Consortium is set up as an independent entity, with Elekta “creating the conditions” for collaboration rather than opting for top-down micromanagement. “Elekta plays an integral role in the Consortium and acts as a facilitator, letting the clinical community define priorities and share their clinical and technical outcomes,” he explains. “Of course, the Elekta product development and engineering teams are also front-and-centre, providing specialist support and training as well as gathering feedback direct from the clinical end-users.”

Down the line, the AHN team plans to work with other Consortium members on multicentre MR-Linac clinical studies – including the application of Unity’s functional MR imaging capabilities. “We get scale when we collaborate, share and analyse our study data together,” Colonias concludes. “If we have multiple Unity clinics contributing MR data on, for example, 100+ patients with pancreatic cancer [versus fewer patients as individual institutions], we can compare post-treatment outcomes and hopefully draw robust conclusions on best practice and treatment efficacy.”