Developments demonstrate consolidation of field strengths at modality's high end
Developments demonstrate consolidation of field strengths at modality's high end
In the early days of MRI, scanner field strengths ran the gamut from the ultralow 0.15T to the largely ignored 2T scanners of Elscint. Of these, 1.5T survived and became the benchmark for high-performance scanning ever since. Vendors have only recently begun exploring new applications that require more signal.
Their new focus on 3T as a standard of excellence in routine clinical scanning has raised the stakes for radiologists. Those in the market for a new system must weigh the still largely unproven benefits of 3T against the risk of investing in a 1.5T scanner that might not be able to meet future needs.
This year, Toshiba America Medical Systems will arrive in Chicago with a new 1.5T platform that company executives say will help establish the company as a leader in high-field MR. The Vantage Atlas, like its predecessor Vantage, will come in two configurations with two different gradients. The X configuration will generate an amplitude of 30 mT/m and a slew rate of 130 mT/m/sec; the Z configuration will generate an amplitude of 33 mT/m and slew rate of 200 mT/m/sec.
The new platform promises routine whole-body imaging through diffusion-weighted imaging technology, a capability dubbed BodyVision that produces a high-resolution map of the body. Atlas will incorporate non-contrast-enhanced imaging, which Toshiba has developed and features on its other Vantage platform, as well as high-resolution breast imaging. Atlas Z will have the horsepower to run cardiac exams.
This year's RSNA show will mark another milestone for the company: the display of its first 3T scanner, the T3. The prototype scheduled for the RSNA exhibit floor is still a ways from commercial production, but it is a clear indicator that Toshiba plans to go head to head with the vendors that have dominated high-performance MR.
"We are looking to make a real technology statement this year at the RSNA," said Bob Giegerich, director of Toshiba's MR business unit.
Along with its Vantage Atlas and 3T prototype, the company will launch an elliptical wide-bore MR scanner similar to the Somatom Espree, which Siemens launched two years ago. The device has a body coil similar to the total imaging matrix (TIM) technology that Siemens introduced in 2003.
The elliptical bore of Toshiba's Vantage Atlas Plus, which will be shown as a work-in-progress, better suits the shape of the human body, Giegerich said. The production unit will have a 50-cm field-of-view, equivalent to its conventional namesake and other similarly designed 1.5T scanners.
The company's body coil will cover a patient 2.05 meters in height and allow 70% of MR exams to be performed feet first, according to Giegerich. With some elements built into the table and others in a typical configuration, the coil comprising up to 128 elements may outshine Siemens' TIM coil, which has a maximum of 76.
At the RSNA meeting, Siemens Medical Solutions will debut the next progression of technology based on TIM, said Nancy Gillen, vice president of the company's MRI division.
Whereas MR tables currently move in three or four steps that position the patient at subsequent stations for scanning, Siemens will show the first results using a patient table that moves continuously into the bore of the magnet.
Applications will be in MR angiography but also in characterization of systemic disease, including cancer, she said.
"It's not so much what we can do today but where this will lead us in the future," Gillen said. "I think we are just scratching the surface."
These plans by vendors exemplify the consolidation of field strengths that has taken place in the 20-some years since MR became commercially available.
"There are large gains to be made if we consolidate engineering and application development efforts on a small number of field strengths," said Michael Wood, Ph.D., general manager of MR research collaboration at GE Healthcare.
At the RSNA meeting, GE will highlight advanced clinical applications. But these are applications that anyone can perform if they have the company's flagship Signa HDx scanner and accompanying hardware or software upgrades. This year, the company will showcase Cartigram, a T2 technique for mapping cartilage. Cartigram provides a noninvasive means of monitoring disease, such as progressive osteoarthritis, and assists in determining the effect of surgical interventions, according to Dave Handler, GE's general manager of MR global marketing. The company also plans to show its Brainwave Fusion package with anatomic, functional, and diffusion-weighted imaging.
"With this package, neuroradiologists and neurosurgeons can visualize in one integrated display the three different areas of imaging that are relevant for neurosurgical planning," Handler said.
Although Siemens, GE, and Toshiba are concentrating their R&D on 1.5T and 3T, Philips Medical Systems is going beyond this range. The company entered the midfield open marketplace in earnest several years ago with the acquisition of Marconi Medical. It continues to offer low- and midfield open scanners.
"But we have elected to augment these with an expensive system, the Panorama 1T, that in our opinion can really hold a candle to the 1.5T system," said Jacques Coumans, Ph.D., vice president of global marketing for Philips MR. "There are no more issues with positioning joints in awkward positions in tunnel systems. The system avoids the feeling of claustrophobia."
Philips will highlight the Panorama 1T at the RSNA meeting for specific applications that are most suited to the open design of the system. Surface coils to be introduced at the RSNA meeting will enhance these or other clinical applications on the 1T product.
The Panorama 1T is getting "very good traction" in European and U.S. markets, Coumans said, but he acknowledged that it is not attracting the high-volume sales of its higher field kin.
Other vendors report that very little is happening at the lower end of the Tesla chain. Toshiba, once a leader in midfield open MR with its superconducting 0.35T platform, has all but dismissed it as a viable product.
"The markets for opens have pretty much dried up," Giegerich said. "Toshiba will be concentrating on 1.5T and 3T from here forward. We think that is where the market is going to go."
Hitachi Medical Systems America, which rose to prominence in the U.S. as a pioneer of open MR, remains a stalwart provider of these systems, updating its top-of-the-line midfield Airis II Elite and 0.7T Altaire to include advanced scanning capabilities, including parallel imaging. The company continues to update the Elite's operating system, having released Ascent 5.0 with new pulse sequences earlier this year and scheduling the latest version, Ascent 5.1, for introduction at the RSNA meeting.
But even Hitachi is hedging its bets. The company introduced its 1.5T Echelon last year. As of September, the Echelon had been installed at four sites, with eight more expected by the end of the year. When pitching the Echelon, the company so far has concentrated on its installed base of open MR customers. Hitachi plans to move beyond that eventually, hoping to raid other companies' customers in the outpatient marketplace.
"We have two differentiators in this marketplace: the reliability and robustness of our products and the knowledge and expertise gained by working with imaging centers, whose needs and requirements tend to be different from hospital environments," said Sheldon Schaffer, vice president and general manager of MR at Hitachi.
Field strength sets the table for the MR community, but the many components within a scanner put the meal on the plate. Toshiba's work-in-progress, Vantage Atlas Plus, will use the same magnet as the basic Atlas version. It's the way the gradients and other pieces are put together that make the elliptical wide-bore scanner and its large field-of-view possible, Giegerich said.
Similarly, the head-to-toe coil pioneered by Siemens, and the version soon to be released by Toshiba, get the most from the fields in which they are immersed. The objective is to accelerate imaging by making studies easier to do. Coils of all types play a role.
One reason why Philips bid $1.3 billion earlier this year for Intermagnetics General was the latter company's superconducting magnet technology, which constitutes the backbone of the Philips MR business. But the deal, which could close by the time Philips arrives at the RSNA meeting, will also bring a treasure trove of surface coils to the company.
"We expect that coils with high channel counts for specific anatomies will be made available at the RSNA for 3T and 1.5T," Coumans said.
Philips was among the first to test the waters of 3T as a routine clinical field strength, yet it avoided the temptation to create long tunnels in favor of compact, lightweight designs. The idea from the start was to make 3T scanners that fit within the space absorbed by a 1.5T scanner. The company's new lightweight 3T scanner, set to be unveiled at the RSNA meeting, has the same footprint as its predecessor, the Achieva 3T.
The new 3T system features a 32-channel architecture offering an improved field-of-view in the z direction, equivalent to the one found on the company's 1.5T systems. This will reduce exam times by covering more area in less time, according to Coumans. The new 3T product will also include cryogen technology that boasts cost savings by minimizing helium boil off.
The company is passionate about maximizing the clinical potential of its systems, he said. Other vendors espouse much the same philosophy in testing and winning the adoption of clinical applications that use their latest developments. The process usually begins by making a new technology available to a few institutions while it is still largely a curiosity.
"Thought leaders then enhance the capability of that technology through particular applications," Wood said. "If it shows great promise, it catches on."
Before achieving widespread adoption, however, new applications must be passed from the hands of highly skilled researchers to mainstream clinical practice. This takes robust technology optimized for the particular field strength and capable of delivering consistent clinical results.