MRI OpenSpeed shakeout turns up vibration problems

July 5, 2000

Unexpected vibrations that turned up in the operation of GE’s new Signa OpenSpeed MRI scanner have put a kink in GE’s efforts to sell the new open-style 0.7-tesla system. The vibration, which causes ghosting to appear in the images, is most

Unexpected vibrations that turned up in the operation of GE’s new Signa OpenSpeed MRI scanner have put a kink in GE’s efforts to sell the new open-style 0.7-tesla system. The vibration, which causes ghosting to appear in the images, is most pronounced when the scanner is sited on flooring not adequately stabilized. GE executives insist, however, that the problem has largely been remedied.

“The bottom line is that it took us a little while to overcome the problem, but we’re ready to roll now,” said Dennis C. Cooke, general manager of global MR at GE Medical Systems.

A big part of the remedy involves the installation of OpenSpeed “on grade,” such that an adequate concrete foundation can mitigate the problem. Hardware and software have also been developed to reduce adverse effects.

Eventually, these fixes in the scanner are expected to be so extensive that special siting requirements will not be necessary. Some time will elapse, however, before that happens.

“For the remainder of this year and for a period next year to be determined, we will not site (OpenSpeed) above the first floor,” Cooke said. “We’ve focused on having a magnet that can be sited anywhere, and we plan on coming out with that enhancement to the OpenSpeed sometime next year.”

The vibration problem was uncovered earlier this year in beta tests at St. Luke’s Medical Center in Milwaukee, a major proving ground and luminary site for GE’s new systems.

The root of the problem is the clamshell-like design of the system. Where some open systems rely on four poles to separate the two magnets, one pole at each corner, GE engineered its OpenSpeed with just two poles, both located at the back of the scanner. During operation, the magnets pull toward each other. This force creates vibration that, unless damped out, creates blurring or ghosting in the images.

Cooke insists that, despite the problem, OpenSpeed remains on schedule for market introduction. The system will be in full production in July, as was predicted at OpenSpeed’s unveiling in November 1999. Deliveries will begin as scheduled in July, Cooke said.

The vibration problem impeded sales efforts, however, as the company decided not to bring prospective customers through the clinical site at St. Luke’s until the problem was fixed. As of the end of June, five customers had visited the site and 70 more were scheduled for visits in the coming months.

Cooke noted that vibration is a relatively common problem in the MRI industry. It particularly occurs in new MRI releases and was found in the company’s flagship Signa products going back to GE’s first 1.5-tesla system introduced in 1984.

Vibration problems have been eliminated on other models and GE’s engineers will eventually fix OpenSpeed, Cooke said. About 80% of the facilities interested in buying an OpenSpeed this year will be able to install one without ghosts resulting from vibration showing up in the images, he said. OpenSpeed should be ready for installation without extraordinary siting requirements by next year.

"What was initially a big technical challenge for us has now become a competitive advantage, because if you’re going to hit the openness that we have gotten, you’re going to have to face this issue," he said. "Solving it is not a short putt."