GE brings high-field MRI to open scanning environments

OpenSpeed combines superconducting, permanent magnet technology

GE Medical Systems has become the first company to debut a true high-field open MRI scanner. The Milwaukee-based company will introduce a 0.7-tesla superconducting scanner featuring an open design next week at the 1999 RSNA meeting. Until now, open systems have been confined to mid field strength units.

GE’s system, called OpenSpeed, achieves high-field capability by mixing materials found in both superconducting and permanent magnets, according to company executives. OpenSpeed received Food and Drug Administration clearance on Nov. 12.

The new product’s magnet comprises two spools of niobium titanium wire, both immersed in liquid helium. These electromagnetic cartridges, separated by stainless steel posts, are positioned above and below the patient. The key to their power is the use of iron disks, which surround the wire spools, to shape the magnetic field and improve homogeneity. Engineers have long known that iron, if used correctly, can boost the power of superconducting materials, said Thomas Penn, NMR program manager. GE has discovered how to harness the power of iron.

This new technology generates a homogeneous field commonly found only on superconducting magnets, a point that Toshiba successfully made on release of its open superconducting system, the Opart, three years ago. Opart, like OpenSpeed, is a superconducting system, but Opart’s 0.35-tesla magnet generates only half the field strength of the GE product. Until the advent of OpenSpeed, Opart was the only open superconducting magnet cleared by the FDA.

Whether the GE system will ultimately cut into sales of Opart depends on how the market responds. The current generation of open systems typically sells for $800,000. At $1.5 million, the OpenSpeed could prove too expensive for these customers. Although GE executives hope the new product will have wide appeal, they expect much of the demand to come from owners of 1-tesla systems.

“While OpenSpeed can serve the expansion market for customers who want another system, it can also serve the replacement market of 1-tesla systems,” said Paul Mirabella, GE vice president and general manager, Americas. “These people paid in excess of $2 million when they bought their current systems.”

A mock-up of what these potential purchasers and others in the imaging community might be buying was shown at a press conference Nov. 17 in New Jersey. Patient access was highlighted, as the OpenSpeed offers a 43-cm gap and a swing table that moves 25º left and right from the magnet’s isocenter. The design makes the scanner especially appealing for pediatric, ICU, trauma, and ER patients, as well as for interventional procedures. But company executives emphasized that OpenSpeed will not be marketed as a specialty product. Rather the system will be positioned for sale as a general-purpose workhorse, capable of completing exams up to three times faster than other commercially available open systems.

GE introduced OpenSpeed to the press ahead of the RSNA meeting, hoping to build excitement about the scanner and to keep it from getting lost in the meeting’s circus-like atmosphere, according to company executives. In doing so, however, the firm had to act before the first clinical system was installed.

At the press conference, two radiologists presented findings about OpenSpeed based on scans done on healthy subjects in engineering bays at GE. Dr. Lawrence Tanenbaum, section chief of MRI at New Jersey Neuroscience Institute, JFK Medical Center-Edison Imaging Associates, in Edison, described OpenSpeed as assuring patient comfort, offering high-field exam times, and providing an enhanced feeling of control.

“It gives an open MR experience that the patient will actually enjoy,” he said.

In addition, the images are high quality, accurate, and expeditiously obtained, according to Dr. Robert Breger, director of MRI at St. Luke’s Medical Center in Milwaukee, where an OpenSpeed was expected to become operational Nov. 22. Breger acknowledged that the ability of a scanner to detect pathology cannot be determined by looking at scans of healthy subjects. He noted, however, that all images share certain characteristics.

“When you look at image quality, you look at contrast-to- noise and the resolution that can be acquired over a specific length of time,” he said. “The initial images (from OpenSpeed) were very high in quality.”

GE will give OpenSpeed special treatment at the RSNA meeting. The company will add a second floor to its RSNA exhibit, place a rotating stage in the center of the 2000-square-foot deck, and plant OpenSpeed in the center of it. It will also be featured in live Webcasts throughout the show. The system is worth the attention, said GE Medical Systems president and CEO Jeffrey Immelt.

“This is truly an open system at high field,” Immelt said. “It has great lines of sight, fast exam time, and high image quality.”

GE will begin production of the system some time in the second quarter of 2000. By the end of that year, company executives hope to have sold 100 of the new systems.

Demand for the system is already beginning to build. At 3 a.m. on Nov. 17, the day of the press conference, GE began taking orders on its Web site, as OpenSpeed became the first MRI scanner to be sold via e-commerce. By the end of the day, GE had received 10 orders.

While interest in the system is expected to soar in the weeks ahead, expectations about its clinical capability may grow beyond the true power of the system. The MRI community has come to expect advanced clinical applications from high-field scanners. They will find few of these on the current version of OpenSpeed, however.

Diffusion-weighted imaging is a work-in-progress and might be included on the system by the time production is up to speed. But single-shot echo-planar imaging (EPI), perfusion imaging, and multislab 3-D time-of-flight MR angiography will likely not be available, precluding advanced functional brain imaging, real-time cardiac scanning, and peripheral angiography. Also absent will be spectroscopy, a capability that mainstream practitioners over the past year have come to expect from a high-field system.

“Out of the gate, the system will not do these exams, but we are looking at them for the future,” said Dennis Cooke, general manager for global MR at GE.

The limiting factor right now is gradient strength. The first system to roll off the production line next year will have an amplitude of 15 mtesla/m and a slew rate of 25. The gradients onboard will serve as the standard configuration, which will soon after be complemented with an option for stronger gradients.

GE executives believe that there are no engineering challenges in the way of boosting the power of OpenSpeed to the next level, which is anticipated to have an amplitude of 25 and a slew of 40. Gradients developed for the Signa Profile, the company’s open mid-field scanner, have a higher amplitude and slew rate than those currently on the OpenSpeed and there is no reason to believe that GE engineers will have any trouble adapting them to run on the new high-field open system.

GE engineers will continue building on this platform, Immelt said. In fact, the company has little choice, since each of the major vendors is known to have an R&D effort of its own focused on the development of high-field open systems. Industry visionaries believe that within the next five to 10 years, the correlation between open configuration and field strength will become unimportant, as open MRI scanners will be available up to, if not beyond, 1.5 tesla.