On Jan. 6, 1996, a six-year-old dog named Kayla made medical history. Having suffered a seizure, she became the first animal to undergo brain surgery with the aid of a unique mobile magnetic resonance imaging system at the National Research Council Institute of Biodiagnostics in Winnipeg. The massive MRI, which moves in to take pictures of the brain while an operation is in progress, helped neurosurgeon Garnette Sutherland pinpoint a tumour and ensure he removed all of it. Three months later, Sutherland, who has spearheaded the development of the world’s first mobile intraoperative MRI, received a card from the dogs gratefid owners. Under a picture of the white-haired Kayla ran the inscription: “Hanging in there, feeling great. Thanks for life.”
Two years ago, Sutherland started using the MRI, now housed at Calgary’s Foothills hospital where he is director of neurosurgery, on human patients. Since then, it has been used in more than 110 surgeries, most involving brain tumours, epilepsy or vascular disease. Sutherland still keeps Kayla’s snapshot in his office, a reminder of the modest beginnings of what has grown into a multimillion-dollar research and business venture—one that promises to dramatically expand the boundaries of neurosurgery. The mobile MRI was recently twinned with a state-of-the-art surgical navigational system developed by a German company, BrainLAB. The MRI’s Winnipeg-based manufacturer, Innovative Magnetic Resonance Imaging Systems, and BrainLAB are now selling their product, dubbed the iMotion, internationally—at prices as high as $5 million. They are also laying the groundwork for the next major step in neurosurgery: robotics. “What we’re doing here,” says Sutherland, “is jumping into the future.” In many ways, the iMotion builds upon two of the most important advances in modern neurosurgery: the invention of computerized tomography (CT) scanning in the 1970s and of MR imaging in the early ’80s. Both have given surgeons unprecedented ability to peer into the brain, with MRIs, in particular, offering highly detailed, three-dimensional snapshots. The problem is that the typical MRI, weighing in at several tonnes, has to be housed outside the operating room because its powerful magnetic fields would wreak havoc on electronic medical equipment. That allows surgeons to take an MR image before and after surgery—but not to confirm during surgery that the job
has been done properly and no bits of tumour remain.
The iMotion grew out of brainstorming sessions between Sutherland and John Saunders, then a Winnipeg-based chemist with the National Research Council, in the early 1990s. How, they wondered, could they bring an MRI into the operating room, then remove it when it was not needed? They hit upon the idea of suspending the five-tonne magnet from a track on the ceiling. When brain images are required, an electric motor wheels out the MRI to surround the patient’s head on the surgical table. At other times, the machine is housed in a compartment off the operating room. To control the MRI’s disruptive magnetic field, they mounted a second magnet perpendicular to the first to cancel out the force field acting outside the unit. That allows standard steel surgical tools and sensitive electronic equipment to stay in the room. The surgical table is made of tita-
With Calgary’s unique MRI on tracks, surgeons can double-check their progress during an operation
nium and glass fibre, materials impervious to magnetism.
With the mobile MRI, Sutherland feels confident during surgery that he is accomplishing what he sets out to do. Typically, brain surgeons must peer through tiny openings. Given the difficulty they have seeing the area where they are working, they sometimes leave a small part of a tumour behind, only to detect it in a post-operative MRI. That often means putting patients through a second operation. Sutherland cites several personal examples to illustrate his point:
• Before he had access to the mobile MRI, he operated on a one-year-old girl suffering from diminished consciousness due to small tumours in the back of her brain. Sutherland removed several of the tumours, but a post-operative MR image revealed that he had missed one. The infant had to undergo a second operation the following week.
• A more recent case involved a 19-year-old with a large tumour in the middle of his head. After delving down between the two halves of the brain, Sutherland was so convinced he had removed all of the tumour that he left the operating room to attend to another matter. But when he returned to close the incision, an MR image had located a small piece of tumorous tissue, which Sutherland then removed.
• A 14-year-old girl had a tumour in her eye that was causing some double vision. Again, the intra-operative MR image after its removal pointed to an undetected piece. It might have taken 10 to 20 years to regrow to the extent that it presented a problem, says Sutherland, but the tumour would ultimately have required further surgery.
The mobile MRI project has received about $20 million in research funding from private and public sources, including a $3.7-million grant from the Alberta government to build an addition to the Foothills hospital to house Sutherlands MRI and a second MRI machine used for stroke research. The makers of the iMotion are negotiating with potential buyers as far afield as San Francisco, Munich and Istanbul.
Other manufacturers have developed intra-operative MRIs in the past three years, but none with the mobility of the iMotion. A so-called Double Doughnut configuration
produced by Milwaukee-based GE Medical Systems allows surgery to be performed within the rings of a large magnet. But the confined space limits the types of procedures surgeons can undertake, and they must operate with instruments made of materials other than steel. Another company, Siemens AG of Germany, has come up with a stationary MRI unit to be installed next to the operating room. That allows an anesthetized patient to be moved to the MRI during an operation—but also poses a potential risk of, among other things, contaminating the surgical field.
Apart from the advantages that a mobile MRI offers, says Sutherland, the addition of sophisticated navigational technology to create the iMotion opens a new world of possibilities. Several markers are placed on a brace that holds the patient’s head. Then the magnet rolls in to take images of the head, the brain itself and the markers. That lets the surgeon calculate the tumour’s exact location. Ultimately, says Sutherland, “what we could then do is tell a robotic arm where to make an incision. A robot will be able to do that more precisely than human eye-hand co-ordination allows.”
That is for another day. For now, Sutherland and his Calgary-based team are content to know they are pushing the neurological envelope. “In our field,” says Sutherland, “the ability to see is a precious thing.” The innovative iMotion is bringing yet another set of eyes to the tricky task of probing the inner brain. C3
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