Neurosurgeons at St. Michael’s use low-field MRI to assist surgeries

TORONTO – Neurosurgeons at St. Michael’s Hospital are among the first in Canada to deploy the Hyperfine Swoop® MR scanner to check on the quality of brain surgeries – right after the procedures and while still in the surgical suite.

The Swoop is a portable, low-field MR – designed for head exams – that can be wheeled into the operating room. It has a field strength of just 0.064T, compared with the 1.5T field strength of a conventional scanner, and it’s much smaller.

That compact size allows it to easily fit into the OR, and the low-intensity of the magnetic field means surgeons can still use their regular metal instruments – something that would be impossible with a full-strength magnetic scanner.

The Swoop scanner enables physicians to see structures in the brain, including tumours and other lesions. It can also be used to spot bleeding or strokes.

It takes just minutes to scan the patient and obtain results.

“It’s amazing to be able to check on the patient with an MR just after you’ve finished operating,” said Dr. Leniel Laud Rodriguez, an internationally trained neurosurgeon working with Dr. Julian Spears, division head of neurosurgery at St. Michael’s Hospital.

“It adds an important measure of safety for the patient and it’s very reassuring for the surgeon,” he added.

Dr. Rodriguez explained that he and his colleagues normally work with pre-op MR and CT scans of a patient’s brain, and they also have navigational aids as they work.

But it sometimes happens that in cancer procedures, the surgeons can’t remove all of the tumour. By imaging right after the procedure, while still in the surgical suite, the team can go back and remove the remaining parts of the tumour or diagnose unforeseen events without delay. That results in a better outcome for the patient.

“For example, sometimes we see tumours that are very well-defined, like a lemon or an orange, and you can easily separate the tumour from the brain,” commented Dr. Rodriguez. “But in other cases, such as gliomas, the tumour has infiltrated the cells … it’s harder to know if we have removed the whole tumour.”

He explained that it’s extremely helpful to be able to image the brain before leaving the operating room, as a quality check.

There are also occasions when an anesthetized patient takes longer to awaken after surgery. With the Swoop on hand, the surgeons can scan right away to see if there has been a complication or if the medication has had a stronger effect than expected.

That’s much better than finishing the procedure and having the patient come back 72 hours later for a follow-up scan, only to discover then that parts of the tumour remains. The patient then must undergo a second surgery.

It also lead to a significant decrease in patient length of stay, which can be prolonged awaiting post operative MRI.

Dr. Rodriguez said he’s done five procedures using the Swoop to check the patients afterwards. He hasn’t had to go back in to remove additional tumours or address any complications, but by checking, it gives the surgeon a real measure of confidence in the procedure.

He believes this way of working could become standard practice in the future.

At St. Michael’s Hospital, surgeons can send the patient for regular MRI imaging, if they are concerned. However, the surgical suites are on the fifth floor and the Radiology Department is on the third floor – it can take a long time to transport the patient for an MRI and to get him or her back.

“So, with this technology, we avoid a step and do the MRI right away in the OR to confirm that we accomplished our surgical goals.” The patient only needs some extra time to wake up from the anesthesia, as there are no concerns with the brain,” he said.

Dr. Rodriguez would like to see the technology taken even further, with additional engineering that allows surgeons to operate while the patient’s head is in the Swoop scanner. This would allow real-time checks on whether the whole tumour is being resected.

While operating, neurosurgeons have many decisions to make. Chief among them is how to avoid important structures in the brain while reaching and resecting tumours. For example, they always want to avoid cutting areas that govern tasks like speech, memory, movement and even the symmetry of the face.

It would also enable the surgeon to reassess the best way to reach a tumour. Sometimes, when the actual surgery is taking place, it turns out that the pre-operative plan isn’t the best way of reaching the lesion.

Surgeons will occasionally come up with a better plan while they’re working, and an MR scan would be very helpful in determining the best path.

“Even though we have navigation and ultrasound, sometimes you have to change your trajectory to reach the tumour,” said Dr. Rodriguez.

With real-time MR imaging assisting the surgery, these decisions would be easier to make, said Dr. Rodriguez.

Current intra-operative MRI technology, which has been available for many years, has the distinct disadvantage that the operating room has to be shielded and all the operative tools must be MRI compatible, which is not the case with Swoop.

“We look forward to the day when Swoop is able to offer this intra operative [while skull is open] dimension,” he said. “If we had this, it would be even more amazing.”

The Hyperfine Swoop is distributed in Canada by UpCare Partners & Associates Inc. of Toronto. The company has deployed the system at hospitals across Canada, including urban centres and the far North. In addition to operating rooms, such as at St. Michael’s, the Hyperfine Swoop has also proven highly valuable in emergency medicine, particularly in remote communities where it is used to rapidly detect bleeds and strokes, helping reduce time to diagnosis and treatment.

Its most common use case, however, has been in the ICU for post-operative follow-up, where it supports ongoing patient monitoring and clinical decision-making.

More recently, Swoop has also made its debut in neurology clinics, including for the management and follow-up of patients with multiple sclerosis (MS).