Medicine: Making the Body Transparent

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Even more dramatic applications may become available as NMR technology improves. Powerful new magnets, chilled with liquid helium to -270° C, not only enhance the images based on hydrogen nuclei, the most prevalent element in the body and the easiest to trace, but also make it possible to pick up nuclear magnetic signals from phosphorus, sodium, fluorine and certain carbon atoms. Doctors are especially excited about the prospect of working with phosphorus, since the energy for all of life's activities comes from chemical reactions involving this element. At the University of Pennsylvania, Dr. Britton Chance has been using phosphorus NMR to diagnose muscular disorders and to study the use of energy in working muscles. His cryogenic magnet is large enough to accommodate only a leg. But, he says, "we are on the verge of sticking the whole body into such magnets. Then we will be able to look at the heart or brain after stroke or injury, not only to see precisely where the damage has occurred but to assess the biochemical capability of the tissue to recover." Such information would greatly aid doctors in choosing a course of treatment.

Versatile though it is, "NMR is not going to replace everything," says Dr. Graeme Bydder of Hammersmith Hospital. "I believe it will have less importance in the abdomen and pelvis because existing techniques, including ultrasound, are very good." Nor is it as good as X ray in depicting fine detail of the bones. Whether the radiation-free technique can reliably detect breast cancer is not yet known, but results with current equipment have been disappointing.

There are also a few practical drawbacks to NMR. Its powerful magnetic field poses a potential hazard to patients with pacemakers and artificial joints and other implants containing metal. NMR costs about 50% more than a CAT: as high as $ 1.5 million for some of the simpler devices, and possibly double that for the strongest cryogenic models. Overhead costs are high too because of the need to house the machine in a huge, metal-free area that is sealed from such outside electromagnetic influences as FM and CB radio. The Cleveland Clinic plans to invest $3 million in a special NMR building.

Still, about 25 U.S. medical centers have NMR machines, on order and, according to General Electric, one of a dozen NMR manufacturers, there will be 150 in place by the end of 1984. Predicts Dr. Theodore Tristan, past president of the Radiological Society of North America: "We're going to see that every large hospital, as its CAT unit wears out, will want to replace it with an NMR system." The challenge then will be to learn how to exploit the tremendous potential of the new techniques. Admits Worthington: "We're just not clever enough yet to appreciate it all."