Deep in a basement at NYU Langone, researchers and engineers are hard at work developing innovative MRI coils — a component whose importance in MRI imaging is all too often overlooked, according to Dr. Daniel Sodickson, professor and director of the Center for Biomedical Imaging at NYU Langone Medical Center.

“If you have a wonderful scanner but a terrible coil, you’ll get a lousy image,” he says. “If you have the right coil, you could boost the performance of the scanner as If you’d paid another million dollars.”

The dedicated RF coil laboratory sports one-of-a-kind prototypes the likes of which you’d be hard- pressed to find anywhere else in the world. Many of them of them are still in the nascent stages of design, slabs of hot glued Styrofoam overlaid with intricate circuitry and wires.

They bear little resemblance to commercial coils, lacking the plastic covering that hides what Sodickson calls “the innards.”

Sodickson shows me one mask-like coil that resembles a device straight out of a science fiction flick. “For the eyes,” he explains with a grin.

Follow the leader
Back in the early 2000s, when manufacturers began to increase the magnetic field strength in their MRI scanners to produce a better signal to noise ratio, something unforeseen happened: researchers noticed that the coils that performed well with low field strengths were no longer well-suited for scanners with higher field strengths.

This is because magnetic fields behave differently at a higher operating frequency. “At some point, the body bends the magnetic frequency like a lens,” explains Sodickson.

Practically speaking, this means when a coil designed for an older scanner is used in a newer, more powerful 7-Tesla machine, it generates images with uneven bright and dark spots because the coil inadvertently registers other properties in the body such as salt content and tissue conductivity.

To address this problem, manufacturers are now starting to create MRI scanners with multiple transmit coils rather than just one — a technology known in the industry as parallel transmission. Using multiple transmitters, doctors can steer the scanner’s magnetic fields and illuminate the bright and dark spots to even out the image.

Scientists hope that multiple transmitters will one day enable them to target a specific area of interest rather than imaging whole slabs of anatomy. “The holy grail is being able to put the signal somewhere exactly,” says Sodickson.

Bent out of shape
The newer 7-Tesla machines also led scientists to another discovery that called long-held assumptions about coils into question.

Coils are called such because they’re just that: a loop of wire similar to the bunny ears on old television sets. Conventional wisdom always held that this was the best shape for optimal MR imaging, but researchers now know that at higher field strengths, coil antennas should look more like cell phone antennas, which are shaped like strips.

By combining strips with loops, researchers are able to capture more signal-to-noise ratio than they could using either of these shapes alone. “It’s a reminder that as the field gets higher, the body goes from being an invisible passive recipient of these fields to becoming an active participant in the behavior of the fields, so we need to account for that,” says Sodickson.

Coils in charge
But these discoveries also led researchers to realize that the body’s tendency to bend the fields at higher field strengths could be an opportunity rather than a nuisance, since the curvature of these fields could help doctors create a noninvasive map of the conductivity and permittivity of the tissue — in other words, the electrical properties of the body.

Electrical properties of the tissue convey important information about the anatomy. Tumors, for instance, have drastically different electrical properties than normal tissue. In fact, the medical community has sought to measure electrical properties of tissue for a long time but lacked the technology to do so — until now.

“So we’re developing a whole new kind of imaging — electrical property imaging,” says Sodickson. “Up till now, coils have been seen as the slaves of the MRI scanners. Their job was just to get you information about the system. Now, higher in frequency, as coils have become richer and richer, they’ve become the mediator of a whole new imaging contrast, a new imaging modality almost,” he adds.

Sodickson brings up one area where such imaging could be useful: currently, electrophysiologists study the electrical properties of the heart by sending a catheter through it. “Down the line in the distant future, if we could do that sort of thing noninvasively from the outside, wouldn’t that be beautiful?” he says.

Channel debate
However, some research trends don’t have an immediate impact on sales, and not everyone in the industry agrees on what constitutes a trend in coils. Though major manufacturers and researchers see higher channel counts as the way of the future, other industry insiders who determine trends based on what they see hospitals buying, beg to differ.

“The biggest trend over the last 12-18 months is the lack of a trend,” claims Randy Walker, vice president of sales at Genesis Medical Imaging/BC Technical, citing the failure of the OEMs to create wider demand for 16 channel coils. “That was supposed to be the latest and greatest opportunity, but we don’t see many being sold or purchased by our users,” he says.

The biggest reason for the failure of 16 channel coils? “You can’t just take an existing room and put 16 channel coils in it,” he says. Upgrading the room to make it 16-channel-compatible is costly, ranging from $100,000-150,000. Given all the economic challenges plaguing hospitals, many of them are understandably skittish about sinking big dollars into a newer technology when their current equipment already gets the job done.

Indeed, this gets at the debate around higher-channel coils and their utility — at what point in the rising channel count are the advantages outweighed by the drawback of extra expense? “The price point has become and continues to be very important to customers. As you go up in channels, the cost is increased quite a bit,” says Andrew Beck, director of business development at MR Instruments.

Higher channels are ostensibly useful because they boost the coil’s signal-to-noise ratio, enhancing image quality. But certain body parts need fewer channels. For example, an abdomen or torso, the largest body parts, would benefit from a higher channel count. On the other hand, for a wrist or a foot, eight or 16 channel counts are just fine, experts like Walker say.

However, NYU’s Sodickson thinks that in the long term, higher channel counts will prevail as a trend. He points out that when he first entered the field, machines in research centers had four to six receiver channels at most. “Guess what people thought the point of diminishing return was for channels back then — four to six!” he laughs. “Then parallel imaging came along and blew that out of the water,” he adds.

His point? The diminishing point of return always shifts over time with the advent of new technology. “It’s an evolving truth,” Sodickson says.

Joint effort
Many manufacturers are now also taking advantages of the opportunities in the underserved pediatric market, making coils specifically designed for younger patients.

Beck explains it’s not uncommon for doctors to adapt an adult’s knee or head coil to image pediatric patients. “They’ll get images, but it doesn’t result in the best patient care,” he says.

“Generally speaking, the closer you put the coils to the anatomy, the better the signal-to-noise ratio you get,” Sodickson says.

Manufacturers also see opportunities in the growing orthopedic market. “I think you’re going to see more imaging on the ankle, possibly the elbow and much more with hips, especially with demographics changing,” says Beck.

From an engineering standpoint, creating coils for joints are more difficult. Coil construction has to be flexible enough to wrap around those areas without sacrificing the number of channels and circuits needed to create a quality image.

Shoulders are an especially challenging part of the body because of their location in relation to the MR scanner’s magnetic field. As the body enters the bore, the quality of the signal diminishes the further away the body gets from the center of the magnetic field — in other words, on the outer sides of the body, where the shoulders are.

“You have to be careful about the physical structure of the coil,” says Beck.

“If there is innovation in the future, it will be eight channel coils in orthopedic use,” says Walker. “The biggest market for MRI in the U.S., aside from neuro imaging, is for orthopedic issues including hip, shoulder and knee replacement.”

Flex points
Flexible coils have also generated more interest lately among budget-conscious hospitals because of their versatility, according to Steve Nichols, COO of NeoCoil. The advantages of having more versatile coils are clear: they’re able to fulfill different functions, eliminating or at least reducing the need to buy dedicated coils for specific parts of the body.

Though flexible/multipurpose coils have been around for a while, a new engineering design that consolidates all the electronics onto the coil antennae instead of a separate interface has resulted in improved image quality.

“Fewer plugs, fewer components to plug in and plug out, and it’s a little less complex to manufacture,” explains Nichols.

A newer kind of flexible coil may be on the horizon as well. Randal Jones, president of ScanMed, hints that the biggest trend he sees for the near future is wearable coil arrays with a large increase in channel count.

“The flexible coils on the market right now are only partly flexible,” explains Jones. “It’s on a rigid base of some sort, but some part of it is flexible. It’s exciting to think of a product line that does more than just semiflex around the anatomy.”

When pressed for specifics on whether he knew of any new products along these lines, Jones was tight-lipped, though he was happy to speculate what such a product would look like. “Maybe we can even use the word elastic to describe it. Elastic is unheard of because it’s hard to stretch metal, and what’s inside coils is metal conductors. Pretty exciting stuff,” he says.

DOTmed Registered MRI Coils Companies

Names in boldface are Premium Listings.
Domestic
Michaelle Serrano, Oxford Instruments Service, LLC, FL
DOTmed 100
Kimberly Wilridge, TCS Match, FL
Randy Cox, MRI Technical Services, Inc., GA
Wes Solmos, Creative Foam Medical Systems, IN
DOTmed Certified
Jeff Rogers, Medical Imaging Resources Inc., MI
DOTmed 100
Andrew Beck, MR Instruments Incorporated, MN
Steve Nichols, NeoCoil LLC, WI
Brian James, North American MRI Parts, CA
Kevin Collins, Signature MRI, CA
Sunny Tabrizi, Sound Imaging, CA
Randall Jones, Resonance Innovations LLC, NE
DOTmed Certified
Edward Sloan Sr., Ed Sloan & Associates, TN
Trent Howell, MIS, GA
Ronen Bechor, ElsMed Ltd. & Relaxation, Inc., FL
DOTmed Certified
DOTmed 100
Bill Erbes, DirectMed Parts, CA
DOTmed Certified
DOTmed 100
Marshall Shannon, Image Technology Consulting, LLC, TX
DOTmed Certified
DOTmed 100

International
Mahmood ElHoor, RBMEng, Jordan