Bruce Sterling - Essays. FSF Columns

beamed through the body in thin, precise slices. The resulting images

are neat cross-sections through the body. Unlike X-rays, magnetic

resonance doesn't ionize and possibly damage human cells. Instead, it

gently coaxes information from many different types of tissue, causing

them to emit tell-tale signals about their chemical makeup. Blood, fat,

bones, tendons, all emit their own characteristics, which a computer

then reassembles as a graphic image on a computer screen, or prints

out on emulsion-coated plastic sheets.

An X-ray is a marvelous technology, and a CAT-scan more

marvelous yet. But an X-ray does have limits. Bones cast shadows in X-

radiation, making certain body areas opaque or difficult to read. And X-

ray images are rather stark and anatomical; an X-ray image cannot

even show if the patient is alive or dead. An MRI scan, on the other

hand, will reveal a great deal about the composition and the health of

living tissue. For instance, tumor cells handle their fluids differently

than normal tissue, giving rise to a slightly different set of signals. The

MRI machine itself was originally invented as a cancer detector.

After the 1946 discovery of magnetic resonance, MRI techniques

were used for thirty years to study small chemical samples. However, a

cancer researcher, Dr. Raymond Damadian, was the first to build an MRI

machine large enough and sophisticated enough to scan an entire

human body, and then produce images from that scan. Many scientists,

most of them even, believed and said that such a technology was decades

away, or even technically impossible. Damadian had a tough,

prolonged struggle to find funding for for his visionary technique, and

he was often dismissed as a zealot, a crackpot, or worse. Damadian's

struggle and eventual triumph is entertainingly detailed in his 1985

biography, A MACHINE CALLED INDOMITABLE.

Damadian was not much helped by his bitter and public rivalry

with his foremost competitor in the field, Paul Lauterbur. Lauterbur,

an industrial chemist, was the first to produce an actual magnetic-

resonance image, in 1973. But Damadian was the more technologically

ambitious of the two. His machine, "Indomitable," (now in the

Smithsonian Museum) produced the first scan of a human torso, in 1977.

(As it happens, it was Damadian's own torso.) Once this proof-of-

concept had been thrust before a doubting world, Damadian founded a

production company, and became the father of the MRI scanner

industry.

By the end of the 1980s, medical MRI scanning had become a

major enterprise, and Damadian had won the National Medal of

Technology, along with many other honors. As MRI machines spread

worldwide, the market for CAT-scanning began to slump in comparison.

Today, MRI is a two-billion dollar industry, and Dr Damadian and his

company, Fonar Corporation, have reaped the fruits of success. (Some

of those fruits are less sweet than others: today Damadian and Fonar

Corp. are suing Hitachi and General Electric in federal court, for

alleged infringement of Damadian's patents.)

MRIs are marvelous machines -- perhaps, according to critics, a

little too marvelous. The magnetic fields emitted by MRIs are extremely

strong, strong enough to tug wheelchairs across the hospital floor, to

wipe the data off the magnetic strips in credit cards, and to whip a

wrench or screwdriver out of one's grip and send it hurtling across the

room. If the patient has any metal imbedded in his skin -- welders and

machinists, in particular, often do have tiny painless particles of

shrapnel in them -- then these bits of metal will be wrenched out of the

patient's flesh, producing a sharp bee-sting sensation. And in the

invisible grip of giant magnets, heart pacemakers can simply stop.

MRI machines can weigh ten, twenty, even one hundred tons.

And they're big -- the scanning cavity, in which the patient is inserted,

is about the size and shape of a sewer pipe, but the huge plastic hull

surrounding that cavity is taller than a man and longer than a plush

limo. A machine of that enormous size and weight cannot be moved

through hospital doors; instead, it has to be delivered by crane, and its

shelter constructed around it. That shelter must not have any iron

construction rods in it or beneath its floor, for obvious reasons. And yet

that floor had better be very solid indeed.

Superconductive MRIs present their own unique hazards. The

superconductive coils are supercooled with liquid helium.

Unfortunately there's an odd phenomenon known as "quenching," in

which a superconductive magnet, for reasons rather poorly understood,

will suddenly become merely-conductive. When a "quench" occurs, an

enormous amount of electrical energy suddenly flashes into heat,

which makes the liquid helium boil violently. The MRI's technicians

might be smothered or frozen by boiling helium, so it has to be vented

out the roof, requiring the installation of specialized vent-stacks.

Helium leaks, too, so it must be resupplied frequently, at considerable

expense.

The MRI complex also requires expensive graphic-processing

computers, CRT screens, and photographic hard-copy devices. Some

scanners feature elaborate telecommunications equipment. Like the

giant scanners themselves, all these associated machines require

power-surge protectors, line conditioners, and backup power supplies.

Fluorescent lights, which produce radio-frequency noise pollution, are

forbidden around MRIs. MRIs are also very bothered by passing CB

radios, paging systems, and ambulance transmissions. It is generally

considered a good idea to sheathe the entire MRI cubicle (especially the

doors, windows, electrical wiring, and plumbing) in expensive, well-

grounded sheet-copper.

Despite all these drawbacks, the United States today rejoices in

possession of some two thousand MRI machines. (There are hundreds in

other countries as well.) The cheaper models cost a solid million dollars

each; the top-of-the-line models, two million. Five million MRI scans

were performed in the United States last year, at prices ranging from

six hundred dollars, to twice that price and more.

In other words, in 1991 alone, Americans sank some five billion

dollars in health care costs into the miraculous MRI technology.

Today America's hospitals and diagnostic clinics are in an MRI

arms race. Manufacturers constantly push new and improved machines

into the market, and other hospitals feel a dire need to stay with the

state-of-the-art. They have little choice in any case, for the balky,

temperamental MRI scanners wear out in six years or less, even when

treated with the best of care.

Patients have little reason to refuse an MRI test, since insurance

will generally cover the cost. MRIs are especially good for testing for

neurological conditions, and since a lot of complaints, even quite minor

ones, might conceivably be neurological, a great many MRI scans are

performed. The tests aren't painful, and they're not considered risky.

Having one's tissues briefly magnetized is considered far less risky than

the fairly gross ionization damage caused by X-rays. The most common

form of MRI discomfort is simple claustrophobia. MRIs are as narrow as

the grave, and also very loud, with sharp mechanical clacking and

buzzing.

But the results are marvels to behold, and MRIs have clearly

saved many lives. And the tests will eliminate some potential risks to