GE prepares to ship next wave of experimental MR therapy scanners

`Double-donut' devices priced at $3 million

GE Medical Systems is poised to launch the next stage of its MR-guidedtherapy program with shipments to 10 investigational sites ofSigna SP, the new designation for the Milwaukee manufacturer'sexperimental "double-donut" scanner.

The new facilities join Brigham and Women's Hospital in Bostonand the University of Zurich in Switzerland as Signa SP test sites.A prototype of the special procedures platform was installed atBrigham and Women's in April 1994. Officials at University Hospitalin Zurich received a scanner in September 1995.

Five systems will be shipped in the next eight weeks, accordingto Mark Augusti, Signa SP marketing and business development manager.The first installation is planned for mid-April, with final deliverycompleted in the first quarter of 1997. Site names will be announcedwhen their systems are installed, Augusti said. As previouslydisclosed, each research facility will pay GE $3 million to participatein the program (SCAN 12/28/94). Augusti is looking for three morecollaborators to increase the installed base to 15 scanners byyear's end. About half of the new systems will be installed inthe U.S. and the other half will go to international sites.

No decision has been made as to whether the unique double-donutdesign will become a commercial product, Augusti said. More experimentalexperience -- perhaps including formal clinical trials -- is neededto demonstrate improved outcomes and clinical efficacy beforethat issue is addressed, he said.

Early anecdotal results are encouraging, however, accordingto Augusti. The time saved by using MR guidance for brain biopsiesat Brigham and Women's is particularly noteworthy. The complexprocedure, which takes up to six hours with the current multi-stepprotocol, is done in less than an hour on Signa SP, Augusti said.

More than a dozen peer-reviewed papers based on clinical experiencewith the device have been published, and numerous studies arein the works. Although limited to the work of a single site, themost promising applications appear to be in neurosurgery and minimallyinvasive endoscopy, Augusti said.

Dr. Stuart Silverman, an interventional radiologist at Brighamand Women's, uses the scanner to guide alcohol ablations of metastaticliver disease. His colleague, Dr. Marvin Fried, has used the machineto guide more than 25 cases of endoscopic sinus surgery.

"In these cases, the tracking system locates the tip ofthe surgeon's endoscopic instrument inside the body and tracksits location in relation to critical structures, such as the opticnerve," Augusti said.

Brigham and Women's researchers are also experimenting withSigna SP for diagnostic examinations of female incontinence. Becauseof the scanner's design, the patient can be scanned sitting upfor contrast-enhanced voiding studies, according to Augusti.

"Seeing that 10 million women develop incontinence eachyear, this application, in particular, has big potential,"Augusti noted.

Orthopedic applications, such as diagnostic studies comparingweight-bearing spines with normal supine spines, are being examinedat Brigham and Women's, Augusti said. Signa SP gained Food andDrug Administration clearance for diagnostic applications lastNovember.

MR-guided TIPS. Although the Zurich researchers have had lesstime with the machine, they are performing body biopsies, spinalimaging, and voiding studies. MR-guided catheter guidance andtransjugular intrahepatic portosystemic shunt (TIPS) proceduresare of particular interest, Augusti said.

Patients can be treated under local or general anesthesia inthe interventional MR suite. Developing MR-compatible anesthesiaand respiratory equipment proved less challenging than creatingnonferric surgical instruments. The biggest challenge so far hasbeen to find MR-compatible instruments that don't create image-degradingartifacts, Augusti said.

GE is working with more than 40 instrument companies to thisend. Surgical microscopes, several endoscopes, and laparoscopicinstruments have been fabricated.

The next set of Signa SP installations features several changesfrom the prototype used at Brigham and Women's, according to Augusti.The diameter of the bore was increased from 55 to 60 cm. The gapbetween the two magnet sections, where the surgeon operates, wasenlarged by 2 cm to 58 cm. Hardware and software that allow SignaSP to track catheters intravascularly were first available onthe University of Zurich's system and will be standard on newscanners, Augusti said.

GE officials have little to say about SP's unique gradientcoil configuration. The system is equipped with flat, separatedgradients that fit on the side of the magnet so they don't interferewith surgery.

"They were no trivial task to design and engineer intoa production system," Augusti said.

The double-donut magnet itself is a 0.5-tesla superconductingdesign. It is built at GE's magnet plant in Florence, SC. Thescanner uses a Signa console and electronics assembled in Milwaukee.Scientists at GE's advanced technology laboratory in Schenectady,NY, built the prototype and handled technology testing. MorryBlumenfeld, who was named general manager of advanced MR developmentat GE earlier this month, manages the project.

"We are now in a preproduction phase in Florence, wherewe can actually see how we would manufacture this and introducesome repeatability into it, if we were to commercialize it,"Augusti said.