When neurosurgeons at the Foothills Hospital of Calgary, Alberta, close a skull after brain surgery, they know exactly what they have accomplished. Two, three, even four times during a complex procedure, the OR team stands back as iMotion, a 1.5-tesla
When neurosurgeons at the Foothills Hospital of Calgary, Alberta, close a skull after brain surgery, they know exactly what they have accomplished. Two, three, even four times during a complex procedure, the OR team stands back as iMotion, a 1.5-tesla MRI scanner, rolls into the room on a suspended track, encircles the head of their patient, bangs out high-resolution images, then retreats behind closed doors.
“It’s a little bit like moving the mountain to Muhammad, but it is a question of safety,” said John Saunders, founder of IMRIS (Innovative Magnetic Resonance Imaging Systems), the company that developed iMotion.
Other surgical suites using intraoperative MRI move the patient rather than the scanner. IMRIS does the opposite because, in at least some instances, the patient should not be moved, neurosurgeons advised IMRIS.
So far, the only patients who can benefit from iMotion are those who go to Foothills Hospital. But Saunders and his colleagues would like to change that. Earlier this year, iMotion was cleared by the FDA. Saunders is now intent on selling the unit to sites in the U.S. and around the world.
BrainLab, a company best known for image guidance and radiosurgery systems, has agreed to be IMRIS’ sales and marketing arm. The Munich, Germany-based company, which has distribution channels in 70 countries, including the U.S., has also taken a 16% equity stake in the Canadian company.
A start-up based in Winnipeg, Manitoba, IMRIS was founded on the observation by Dr. Garnette R. Sutherland, a neurosurgeon at the University of Calgary, that MRI could improve the planning and monitoring of complex neurosurgery. Sutherland made the comment to Saunders, who was then a researcher at Canada’s National Research Council Institute for Biodiagnostics. The idea simmered as a pilot research project at NRC, then took hold after Saunders founded IMRIS.
As installed at Foothills Hospital and cleared by the FDA, iMotion is composed of some of today’s most advanced technology. The cornerstone of the system is a short-bore magnet measuring 1.4 meters and featuring a patient aperture of 72 cm. A self-shielded gradient coil operates at 25 mtesla per meter with a 300-microsecond rise time. A digital, high-powered radio-frequency system supports rapid, high-quality scans, including fat saturation and echo-planar imaging. Advanced shimming produces a highly homogeneous field. Active shielding decreases the fringe field, restricting the 5-gauss line to a radius of under three meters - tight enough that OR walls need not be modified.
The magnet comes from GE Medical Supplies Oxford. Surrey Medical Imaging Systems, prior to its acquisition by Marconi Medical Systems, helped develop the imaging console. Marconi supplies many of the electronics, including gradients, and the software (Via Scan Suites for neuro, body, and musculoskeletal imaging, as well as MR angiography).
Sure to limit customer appeal is the price - $2.5 million. Also worth considering is the site preparation, namely the installation of a ceiling-suspended track upon which the scanner rides. If it is installed to serve a single operating room, IMRIS recommends the construction of a “closet” to house the scanner after each use.
Included as part of the system is an MRI-compatible OR table. This table, developed mostly by IMRIS engineers, is designed to support a range of neurological interventions. It can handle a patient as large as 440 pounds or as small as an infant. Accessories, such as an MRI-compatible skull clamp, are built into the table, which can tilt and roll in just about any way imaginable.
Integrated with iMotion is a BrainLab VectorVision image-guided surgical system. Data acquired during the MRI scan are transferred to VectorVison over a high-speed link, first for use in surgical planning, then to update the 3-D model for intraoperative navigation.
“One of the problems with neurosurgery is that after awhile, brain shifts occur (as the tumor is removed), so the navigational devices become inaccurate,” Saunders said. “But if you take images periodically, you can recalibrate.”
Sterilization is not an issue for iMotion. Rather than try to sterilize the scanner, a plastic bag resembling a giant condom, according to Saunders, is placed over the patient’s head. The magnet is brought in, the scan is completed, the magnet is withdrawn, and the bag is removed.
Most remarkable is the versatility of this ceiling-suspended MRI. Different configurations have been laid out involving a single operating room, dual ORs, and a single OR with an adjoining diagnostic suite. In each scenario, iMotion moves from behind closed doors to appear tableside in less than a minute.
In a single OR, the configuration at Foothills Hospital, iMotion spends most of its time tucked away in an oversized closet, out of the surgical team’s way. The scanner is called in two to four times during surgery and ushered out each time after completing the individual scans.
While optimal for the surgical team, a single-room, dedicated neurosurgical MRI might be difficult to justify because of the cost. Two ORs with a closet in between might be a little easier, as the system can move in and out of either room. Each OR would need a patient table, RF head coil, and display monitors, but a single control room would operate the scanner in either room.
Most appealing, according to Saunders, may be the combination of an OR and diagnostic suite, as routine scans could generate revenue when the scanner is not needed during surgery. This configuration eliminates the closet, since the scanner would simply reside in the diagnostic suite until needed in the neighboring OR. Another difference would be the use of a standard patient table in the diagnostic area rather than one specially designed for surgery.
Two-room combinations are not the only possibilities. Because iMotion is ceiling-suspended, a track system might link three or more rooms. Ultimately, the user must decide which configuration to choose.
But regardless of how many customers sign up or which configurations they choose, iMotion has gotten intraoperative MRI off the ground.