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Bruce Sterling. Magnetic Vision


bruces@well.sf.ca.us Literary Freeware: Not For Commercial Use
From THE MAGAZINE OF FANTASY AND SCIENCE FICTION, April 1993. F&SF, Box 56, Cornwall CT 06753 $26/yr USA $31/yr other F&SF Science Column #6: "Magnetic Vision" Here on my desk I have something that can only be described as miraculous. It's a big cardboard envelope with nine thick sheets of black plastic inside, and on these sheets are pictures of my own brain. These images are "MRI scans" -- magnetic resonance imagery from a medical scanner. These are magnetic windows into the lightless realm inside my skull. The meat, bone, and various gristles within my head glow gently in crisp black-and-white detail. There's little of the foggy ghostliness one sees with, say, dental x-rays. Held up against a bright light, or placed on a diagnostic light table, the dark plastic sheets reveal veins, arteries, various odd fluid-stuffed ventricles, and the spongey wrinkles of my cerebellum. In various shots, I can see the pulp within my own teeth, the roots of my tongue, the boney caverns of my sinuses, and the nicely spherical jellies that are my two eyeballs. I can see that the human brain really does come in two lobes and in three sections, and that it has gray matter and white matter. The brain is a big whopping gland, basically, and it fills my skull just like the meat of a walnut. It's an odd experience to look long and hard at one's own brain. Though it's quite a privilege to witness this, it's also a form of narcissism without much historical parallel. Frankly, I don't think I ever really believed in my own brain until I saw these images. At least, I never truly comprehended my brain as a tangible physical organ, like a knuckle or a kneecap. And yet here is the evidence, laid out irrefutably before me, pixel by monochrome pixel, in a large variety of angles and in exquisite detail. And I'm told that my brain is quite healthy and perfectly normal -- anatomically at least. (For a science fiction writer this news is something of a letdown.) The discovery of X-rays in 1895, by Wilhelm Roentgen, led to the first technology that made human flesh transparent. Nowadays, X-rays can pierce the body through many different angles to produce a graphic three-dimensional image. This 3-D technique, "Computerized Axial Tomography" or the CAT-scan, won a Nobel Prize in 1979 for its originators, Godfrey Hounsfield and Allan Cormack. Sonography uses ultrasound to study human tissue through its reflection of high-frequency vibration: sonography is a sonic window. Magnetic resonance imaging, however, is a more sophisticated window yet. It is rivalled only by the lesser-known and still rather experimental PET-scan, or Positron Emission Tomography. PET- scanning requires an injection of radioactive isotopes into the body so that their decay can be tracked within human tissues. Magnetic resonance, though it is sometimes known as Nuclear Magnetic Resonance, does not involve radioactivity. The phenomenon of "nuclear magnetic resonance" was discovered in 1946 by Edward Purcell of Harvard, and Felix Block of Stanford. Purcell and Block were working separately, but published their findings within a month of one another. In 1952, Purcell and Block won a joint Nobel Prize for their discovery. If an atom has an odd number of protons and neutrons, it will have what is known as a "magnetic moment:" it will spin, and its axis will tilt in a certain direction. When that tilted nucleus is put into a magnetic field, the axis of the tilt will change, and the nucleus will also wobble at a certain speed. If radio waves are then beamed at the wobbling nucleus at just the proper wavelength, they will cause the wobbling to intensify -- this is the "magnetic resonance" phenomenon. The resonant frequency is known as the Larmor frequency, and the Larmor frequencies vary for different atoms. Hydrogen, for instance, has a Larmor frequency of 42.58 megahertz. Hydrogen, which is a major constituent of water and of carbohydrates such as fat, is very common in the human body. If radio waves at this Larmor frequency are beamed into magnetized hydrogen atoms, the hydrogen nuclei will absorb the resonant energy until they reach a state of excitation. When the beam goes off, the hydrogen nuclei will relax again, each nucleus emitting a tiny burst of radio energy as it returns to its original state. The nuclei will also relax at slightly different rates, depending on the chemical circumstances around the hydrogen atom. Hydrogen behaves differently in different kinds of human tissue. Those relaxation bursts can be detected, and timed, and mapped. The enormously powerful magnetic field within an MRI machine can permeate the human body; but the resonant Larmor frequency is 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 the patient, and put the physician on surer ground with his diagnosis. So why not just go ahead and take the test? MRIs have gone ahead boldly. Unfortunately, miracles rarely come cheap. Today the United States spends thirteen percent of its Gross National Product on health care, and health insurance costs are drastically outstripping the rate of inflation. High-tech, high-cost resources such as MRIs generally go to to the well-to-do and the well-insured. This practice has sad repercussions. While some lives are saved by technological miracles -- and this is a fine thing -- other lives are lost, that might have been rescued by fairly cheap and common public-health measures, such as better nutrition, better sanitation, or better prenatal care. As advanced nations go, the United States a rather low general life expectancy, and a quite bad infant-death rate; conspicuously worse, for instance, than Italy, Japan, Germany, France, and Canada. MRI may be a true example of a technology genuinely ahead of its time. It may be that the genius, grit, and determination of Raymond Damadian brought into the 1980s a machine that might have been better suited to the technical milieu of the 2010s. What MRI really requires for everyday workability is some cheap, simple, durable, powerful superconductors. Those are simply not available today, though they would seem to be just over the technological horizon. In the meantime, we have built thousands of magnetic windows into the body that will do more or less what CAT-scan x-rays can do already. And though they do it better, more safely, and more gently than x-rays can, they also do it at a vastly higher price. Damadian himself envisioned MRIs as a cheap mass-produced technology. "In ten to fifteen years," he is quoted as saying in 1985, "we'll be able to step into a booth -- they'll be in shopping malls or department stores -- put a quarter in it, and in a minute it'll say you need some Vitamin A, you have some bone disease over here, your blood pressure is a touch high, and keep a watch on that cholesterol." A thorough medical checkup for twenty-five cents in 1995! If one needed proof that Raymond Damadian was a true visionary, one could find it here. Damadian even envisioned a truly advanced MRI machine capable of not only detecting cancer, but of killing cancerous cells outright. These machines would excite not hydrogen atoms, but phosphorus atoms, common in cancer-damaged DNA. Damadian speculated that certain Larmor frequencies in phosphorus might be specific to cancerous tissue; if that were the case, then it might be possible to pump enough energy into those phosphorus nuclei so that they actually shivered loose from the cancer cell's DNA, destroying the cancer cell's ability to function, and eventually killing it. That's an amazing thought -- a science-fictional vision right out of the Gernsback Continuum. Step inside the booth -- drop a quarter -- and have your incipient cancer not only diagnosed, but painlessly obliterated by invisible Magnetic Healing Rays. Who the heck could believe a visionary scenario like that? Some things are unbelievable until you see them with your own eyes. Until the vision is sitting right there in front of you. Where it can no longer be denied that they're possible. A vision like the inside of your own brain, for instance.

Last-modified: Sat, 23 May 1998 08:27:15 GMT
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