Toshiba plans U.S. introduction ofsuperconducting open MRI scanner

Opart's launch accompanies retirement of low-field Access

Toshiba America MRI will soon introduce a new MRI platform thathas the potential to be its most important MRI product launchever, and the company is retiring the MRI scanner that has madea notable contribution to the advancement of the technology.

Toshiba's 0.35-tesla Opart has the dual distinction of beingan open-style superconducting scanner and a cryogenless superconductingmagnet. GE Medical Systems also has developed an open superconductingMRI scanner, Signa SP, which is being used for research applicationsrather than as a commercial product.

Opart is awaiting 510(k) regulatory clearance and will be displayedfor the first time in the U.S. next month as a work-in-progressat the Radiological Society of North America conference. The systemwill begin shipping to Japanese customers in December.

Absent from the Chicago exhibition for the first time sinceits roll-out in 1987 will be the 0.064-tesla Toshiba Access, theindustry's first open MRI system. John Ariatti, vice presidentof marketing, announced the retirement of the venerable systemlast week. Sales and manufacturing have ceased, and only a fewAccess scanners are left in inventory, he said.

Toshiba will continue to sell accessories, such as radio-frequencycoils, and will provide service and technical support for Access,according to Ariatti. With the exception of previously announcedsoftware enhancements, however, the company has halted productdevelopment for Access, he said.

At the same time, Toshiba is expanding to record levels theproduction capacities of its Applied SuperConetics (ASC) magnetplant in San Diego and its MRI scanner assembly facility in SouthSan Francisco, CA.

"We're pushing them beyond what they've ever done beforein production," Ariatti said.

The effort stems from the Japanese response to Opart, whichwas introduced at the Japan Federation of Medical Congress Promotionin April (SCAN 4/10/96). Units destined for export to Japan willmonopolize South San Francisco production until at least mid-1997.At that point, the company will begin addressing the accumulatedU.S. backlog. After the U.S. launch, Opart will be introducedin phases in Europe and the rest of the world, Ariatti said.

Two economic benefits will be stressed when Toshiba marketsOpart to U.S. customers, Ariatti said. Opart will cut costs becausecryogens are not needed, and downtime will be eliminated becausecryogens need not be replenished, he said. Image quality willbe a major selling point, along with traditional arguments aboutopen MRI serving claustrophobic and pediatric cases.

Through focus-group research, Toshiba's marketing staff haslearned that Opart will be perceived by U.S. customers as competitionfor high-field supercons at least as often as it is viewed asa rival for open-style MRI electromagnet and permanent-magnetplatforms sold by Hitachi, Siemens, Picker, GE, and Fonar.

"Universities that have high-field systems are tellingus that over 90% of the patients by U.S customers they do on theirhigh-field scanners could be done on this unit," Ariattisaid.

The four-post configuration of Opart is similar in appearanceto Toshiba's Access. Opart features the same RISC-based workstationarchitecture and graphical user interface found on Flexart andVisart, Toshiba's mid- and high-field scanners.

Innovations featured on Opart stem from a two-stage Gifford-McMahon(GM) cryocooler supplied by Leybold Cryogenics North America inHudson, NH. The breakthrough performance of this electrical refrigerationsystem was derived from pioneering work at Toshiba's central laboratoryin Kawasaki, Japan. Scientists there discovered that a GM cryocoolercould maintain temperatures as low as 4°K when erbium-3 nickelwas used in the cryocooler's regenerator. U.S. Navy researchersworking on a superconducting magnet for a minesweeper later foundthat neodymium -- another rare-earth element -- is a cheaper andmore durable regenerating material.

Opart's cryocooler is 2 feet long and about 6 inches in diameter.It weighs 35 pounds and is connected by a helium gas line to acompressor that is roughly the size of a two-drawer file cabinetand is installed outside the imaging suite. The magnet is containedinside a vacuum cryostat, like other superconducting MRI magnets,but it operates without a helium cryostat, making it smaller,lighter, and cheaper to run, according to Toshiba America MRIchief scientist Dr. Leon Kaufman.

Opart is also equipped with an iron-core superconducting magnet.Although iron-core magnets are heavier than their air-core competition,Toshiba engineers chose the configuration to reduce system sizeand complexity, Kaufman said.

Additional performance enhancements come from the pole tips'lack of eddy currents. Toshiba eliminated eddy currents by usinglaminated pole tip material that breaks up conducting paths whereeddy currents form. By solving the eddy current problem, the designerswere able to do without gradient self-shielding and to positionthe gradient coils closer to the patient. Opart is equipped with10-mtesla/m gradient coils and operates at rise times of about0.5 msec, Kaufman said.