On a quest to create the next generation of MRI machines, CWRU physicists have helped discover a breakthrough. Think the social interactions among human beings are complex? They're nothing compared to the demanding etiquette being forced upon electromagnetic fields by a team of scientists associated with the Department of Physics at Case Western Reserve.

Robert Brown, the Institute Professor of Physics, and Shmaryu Shvartsman, senior research scientist, insist that the electromagnetic fields used in magnetic resonance imaging (MRI) "dance together," but the researchers won't allow some of the wired cylindrical coils that create them to "talk" to each other. In fact, they want to "decouple" these coils completely. Sounds like a dysfunctional two-step!

Actually, this playful language describes a breakthrough called "supershielding" that could not only transform the design of conventional MRI machines but also improve the design of other devices that use electromagnetic fields. Prof. Brown and Dr. Shvartsman and three alumni working at Cleveland's Picker International--Michael Morich (GRS '87 and '93, electrical engineering and applied physics), Labros Petropoulos (GRS '93, physics), and Hiroyuki Fujita (GRS '98, physics)--have discovered a revolutionary method for containing the powerful fields created by an upcoming generation of smaller, more patient-friendly MRIs. In this model, the MRI fields--some of which are 10,000 times as strong as the Earth's magnetic fields--won't wreak electromagnetic havoc outside the MRI room, on the credit cards, hand-held computers, or pacemakers of people inside the room, or even within the machine's own tightly wired innards.

"We were going over the mathematics, and, all of a sudden, a whole new way of looking at the problem appeared," says Prof. Brown, jumping from his chair to draw an MRI coil on a conference room blackboard in the Rockefeller Building. He ends his sketch with a flourish of chalk dust at the outer edge of the coil, which looks something like an open-ended can of pop wrapped with wire. "It means that the electromagnetic field will be almost zero from this coil outward. It's a real paradigm shift. And it's a wonderful thing."

The scientists have already presented a paper on their work at the International Society for Magnetic Resonance in Medicine, held in Philadelphia in May. In addition, Picker and the scientists have applied for a patent for supershielding, which will allow Picker the rights to medical imaging applications and CWRU the rights to nonmedical applications.

Since he joined the CWRU faculty in 1970, Prof. Brown has worked on various projects with Picker, a leading producer of medical diagnostic imaging equipment and the world's largest supplier of radiological supplies and accessories. Including Drs. Morich, Petropoulos, and Fujita, seven of his former students are now employed there, making Picker the largest local employer of CWRU-trained physicists. Still, the collaboration between Prof. Brown, Dr. Shvartsman, and Picker might appear to be an odd match, as the CWRU pair specializes in the kind of elementary particle physics that seems otherworldly to most people and certainly beyond the scope of a manufacturing company. The two scientists spend much of their time pondering the structure of both huge galaxies and the tiny neighborhoods of quarks within protons, as well as tracking the mathematical underpinnings of the "cosmic strings" that some physicists believe were cast into space after the Big Bang.

"It seems far away from real life," Prof. Brown says. "I actually hate that term, because this stuff is real life, too. But what we bring from particle physics is the ability to work on hard mathematical problems. With things becoming more high-tech in industry, you need more and more sophisticated mathematics. If you want to improve a product, you find its qualities, quantify its qualities, and make them better using mathematical models."

An Open Question

Three years ago, Drs. Morich and Petropoulos brought the physics department the company's toughest conundrum yet. Picker wanted to develop a new line of MRIs that were more compact than the traditional, pop-can-shaped machines, but more powerful and accurate than the so-called "open" MRIs--which come in a variety of less confining shapes--now used in some places. The new machines would relieve the discomfort of patients whose claustrophobia makes it nearly unbearable for them to undergo scanning in the long, dark barrel of today's cylindrical MRIs. In addition, the reduced-length machines would give physicians the opportunity to perform surgery while the imaging is taking place.

Upon first considering this new kind of MRI, there seemed to be no way to make the cylindrical machine shorter without its magnetic fields bulging out of the ends. Even today's longer MRIs have a certain amount of leakage. Though the leakage doesn't pose a health hazard, institutions can pay up to $300,000 to line the walls of an MRI room with iron so that the magnetic fields don't wipe out the memory of computers on another floor or give off a signal that interferes with commercial radio and TV stations. But when the two Picker scientists tried to develop a mathematical formula on which to base the design of the more compact machines, their equations showed that the magnetic fields would literally gush out the ends.

A traditional MRI machine is like a giant cylindrical onion comprising three kinds of coils embedded with wire: On the outside is the main coil, which encloses three gradient coils, which enclose a radio-frequency coil at the center of the machine. Each of these so-called primary coils generates a different kind of magnetic field when current flows through the wire. These magnetic fields excite the body's hydrogen atoms in particular ways and help produce an image from the way the atoms react.

Even though some of these coils are activated during the same period of time, their fields must not interact with, or "talk to," each other, or else the image can be ruined. To keep them from interacting, each of the primary coils is surrounded by yet another coil, called a secondary coil. The secondary coils create magnetic fields, too, but these fields are designed to contain the fields from the primary coils to a limited area and keep them from interfering with each other, as well as spilling outside.

However, this method for containing the magnetic fields has only worked on machines of a certain length. For one thing, a primary coil's magnetic field is strongest at or near its center, and it grows weaker toward the ends of the coil; with a shorter coil, the ends are closer to the center, so the field is harder to contain. In addition, the Picker scientists must generate stronger fields within the new, smaller coils to obtain the same quality image as that derived from the longer coils. With stronger electric currents flowing around shorter coils, there is even greater potential for leakage.

"With a shorter coil, you have to make everything work harder," Prof. Brown explains. "We still have to produce a big enough field to do the same kind of imaging, but the shielding has to get shorter along with the coil. It's like making the umbrella smaller but your body stays the same size. It won't work--the umbrella won't keep your shoulders dry."

A Mighty Shield

When the Picker scientists and the CWRU team first met to discuss the problem, they thought they might find the answer--if there was one--by pounding away at the same equations that had given them the most effective design for today's longer coils.

"We started with Maxwell's equations," says Dr. Morich, referring to James Clerk Maxwell, a nineteenth-century Scottish physicist who is considered the father of electromagnetic theory. "We always start there, because he laid the original mathematical foundation for the behavior of electric and magnetic fields. All the mathematical equations that are used to calculate anything related to these fields are based on his equations, which have been experimentally validated for a long time."

In the past, scientists have applied Maxwell's equations to MRI design by positing the theoretical existence of a perfect secondary coil, meaning one that was infinitely long, and determining how much current and what kind of coil arrangement it needed to contain the field from the primary coil. Then, these numbers in hand, the scientists would impose a constraint on the equations--that of a finite-length secondary coil--and adjust the currents to fit the real-life dimensions of the shield. However, this standard method worked, with an acceptable level of imperfection, only for a coil of a certain minimum length--not for the much shorter coils Picker wanted for its new line of MRIs. "One would mutilate the answer," Prof. Brown says. "You would try to cut and squeeze those currents to fit the shorter coil. The field leaks out because of that mutilation."

Still, the team continued to struggle with the problem--Prof. Brown, Dr. Shvartsman, and Dr. Fujita (then a graduate student) at CWRU, and Drs. Morich and Petropoulos at Picker. Finally, after months of staring at numbers that didn't seem to lead anywhere, inspiration struck. "It was as if an apple fell on our heads," Dr. Shvartsman says, echoing a tone of incredulity that all the members of the team share. "We realized that we had to add another ingredient to kill the outside field. We wound up discovering some new consequences to Maxwell's equations."

The scientists understood that they needed to impose yet another constraint on the equations. Not only did the infinite secondary coil have to become a finite one, but the fact that the primary coil was itself finite had to be imposed explicitly as an equation. When they added this final constraint, something interesting happened. The equations dictated that the current had to change not only on the secondary coil but also on the primary coil, which everyone had assumed to be unfazed by the shielding constraints. When both coils changed in the right ways, the result was amazing: great shielding everywhere. In fact, once the right changes were made to the primary coil, causing it to generate both positive and negative current, it worked as a system with the secondary coil--they "danced" together--to contain the field. Of course, the shielding would be reduced when real, bumpy wires were substituted for smooth theoretical current. Nevertheless, the results were still much improved.

Overall, this new supershielding is up to 100 times more effective than the old, standard method of shielding. In this new paradigm, it doesn't seem to matter how long the secondary coil is--it can even be smaller than the primary coil. Using Prof. Brown's umbrella analogy, the secondary coil can shrink to the size of a tiny cocktail umbrella, but it will shield someone from the rain just as well as those huge umbrellas that bloom all over a baseball stadium when clouds threaten the game. The secret is that, for a very small secondary coil, the primary coil helps out with a certain amount of self-shielding.

Prof. Brown points out that in every advance, there is a trade-off. In this case, the newly imagined primary coils will be more complicated to engineer and manufacture, requiring currents that are about fifty percent stronger than before. However, the Picker scientists are confident that improvements in manufacturing will keep pace with this new design and other innovations. "Five or ten years ago, the way we manufactured coils was different from the way we manufacture them now," says Dr. Petropoulos. "New solutions make us explore new kinds of manufacturing."

The team has finished the design for supershielding the MRIs' gradient coils and is now working on supershielding for a complete MRI system. Since Maxwell's equations for electromagnetism have been experimentally validated for more than a century, their careful calculations and computer modeling are enough to convince Picker that the approach is feasible. Prof. Brown estimates that the company will introduce its new line of more compact, completely supershielded MRIs in about two years.

Anything and Everything

The new supershielding concept has been greeted with shock--and then amazed acceptance--by others outside the CWRU-Picker partnership. One of the first outside experts who studied the results was Mark Haacke, director of magnetic resonance imaging research at the Mallinckrodt Institute of Radiology at Washington University in St. Louis. While Dr. Haacke says that he himself wasn't a scoffer, he can understand how others might have a hard time adjusting to this new paradigm.

"Sometimes, those of us in science are very ingrained in what we're used to," says Dr. Haacke, who can already think of several potential applications for supershielding beyond its use in MRI. "When a new idea like this comes along, a lot of people will be skeptical. I think what [the CWRU-Picker team has] done is truly visionary. We probably won't even discover half the uses for this for another five or ten years, but I think it's very exciting."

For Prof. Brown, the supershielding breakthrough is yet more evidence of the wonders one can do with physics. He is often summoned to ply his trade by a wide range of people wanting solutions to their problems. Last year, reporters called all summer long asking him to compute the probability of baseball slugger Mark McGwire's breaking the home-run record. A lawyer involved in a liability case has asked him to mathematically model the way in which way his client fell off a ladder. An art professor is hoping that Prof. Brown can help in understanding the so-called fractal patterns inherent in the paintings of Jackson Pollock. A plastic surgeon has even asked him to develop mathematical models for breast reduction surgery.

"Everyone thinks physicists know everything," Prof. Brown says, waving at the non-theoretical ladder that peeks out from behind a table in the Rockefeller Building. "We sure don't, but I'm forever getting calls. Physics is a wonderful thing, because it allows you to think about anything and everything. Physics is just a wonderful life."

Kris Ohlson's last story for CWRU Magazine was "The Wonder of Science," in the winter 1999 issue.

Photography by Michael sands, cwru. Drawings courtesy of the researchers.