Functional MRI could lead to 4-tesla renaissanceThe nuclear magnetic resonance instrument division of Varian Associatesin Palo Alto, CA, is chiseling out a specialized niche in ultra-high-fieldMRI with the launch of Unity Inova, a whole-body
The nuclear magnetic resonance instrument division of Varian Associatesin Palo Alto, CA, is chiseling out a specialized niche in ultra-high-fieldMRI with the launch of Unity Inova, a whole-body scanner availablein 3- and 4-tesla configurations for functional imaging and spectroscopy.
Robarts Research Institute in London, Ontario, bought the firstInova late last year, according to Alan Rath, imaging productmanager at Varian. The 4-tesla scanner will be installed in mid-April.The Unity Inova project was unveiled at the Radiological Societyof North America meeting in November (SCAN 11/22/95).
Purchase agreements with several other institutions have beensigned, Rath said. Oxford University in the U.K. ordered a 3-teslasystem in January, and Rath expects an order for a 4-tesla modelfrom a Japanese brain research institute by the end of this month.The 4-tesla version of Inova costs $3 million to $4 million, Rathsaid.
Unity Inova capitalizes on improvements in spectrometer andgradient coil design made since Varian's first generation of 4-teslascanners was installed in 1990, Rath said. It is fabricated aroundadvanced spectrometer and console design developed by Varian anda 4-tesla superconducting magnet and gradient coil technologycontributed by Siemens Medical Systems. The gradient coils andassociated electronics were derived from 25-mtelsa/m gradientcoils originally developed for the Siemens 1.5-tesla Vision.
"Inova provides a very flexible, programmable system thatis capable of really thriving in a research environment. We areoffering something that readily adapts to new techniques,"Rath said.
These investigational instruments are not subject to Food andDrug Administration premarket review. The FDA has approved theuse of 4-tesla field strength magnets for in vivo adult researchunder specific conditions, according to Rath. The purchaser'sinternal review board addresses safety and ethical questions.
Although better known in radiology circles for its radiationtherapy equipment, Varian has been a world leader in sales ofanalytical spectroscopy systems since the technology first emergedfrom the laboratory, Rath said. Varian sold the first commercialinstrument for chemical analysis in 1952.
Most of Varian's sales relating to nuclear magnetic resonanceimaging derive from its chemical spectrometer sales. The companybegan building high-field small-bore scanners for in vivo animalstudies in 1985.
Revisiting a niche. Inova is Varian's second major thrust intothe medical MRI arena. The first effort also revolved around ultra-high-fieldtechnology. The work was undertaken by Spectroscopy Imaging Systems(SISCO), a joint venture between Varian and Siemens. SISCO mainlybuilt research-grade, small-bore scanners for in vivo animal studies.The joint venture shipped about 60 small-bore machines to customersaround the world. Field strengths ranged from 2 to 9.4 tesla,Rath said.
SISCO engineers subsequently assembled two commercial 4-teslawhole-body systems. One of those has operated since 1990 at theUniversity of Minnesota in Minneapolis under the direction ofDr. Kamil Ugurbil, director of the university's center for MRIresearch. The other system ran at SISCO's Fremont, CA, laboratoryfor several years before its sale to Brookhaven National Laboratoryin New York. It was installed earlier this year.
GE and Philips have also dabbled with 4-tesla field strengthequipment, Rath said. GE built an ultra-high-field scanner operatingat the National Institutes of Health laboratory. GE is also collaboratingwith Advanced NMR in the manufacture and sale of ultra-high-fieldsystems for research applications (SCAN 6/1/94). Philips' singleeffort in this ultra-high-field class was installed at the Universityof Alabama in Birmingham, Rath said.
The SISCO joint venture dissolved in early 1992 just as theresults of the first major experiments on functional MRI usingits scanner were coming to light, according to Rath. He notedthat research interest in 4-tesla technology has grown steadilysince then because these scanners are inherently better than 1.5-teslasystems for functional research work. The physical mechanismsthat make functional imaging possible are field-dependent, meaningthat resolution improves as field strength increases. Magneticsusceptibility, a key to measuring the distribution of oxygenatedblood in the brain, is directly proportional to the strength ofthe magnetic field, he said.
"You have quite an enhancement. If you look at a typicalpaper that describes functional imaging at 1.5 tesla versus 4tesla, you can see that difference easily," Rath said.
To a lesser extent, these findings also apply to the investigational3-tesla scanners manufactured by GE and Advanced NMR as well asthose made by German manufacturer Bruker Instruments. The GE/ANMRjoint venture announced the sale of three 3-tesla scanners toJapanese customers last November.
Rath anticipates that research interest in functional imagingwill lead to a second wave of ultra-high-field installations.
"There will be 20 to 30 new installations in the nextyear or two. With that increase, you'll see an explosion of functionalimaging research and more explorations into spectroscopy researchas well," he said.