Medicine: Triumph of the Odd Couple

They share a Nobel Prize for pioneering the CAT scanner

They had never met, never corresponded. But on opposite sides of the Atlantic, U.S. Physicist Allan Cormack, 55, of Tufts University, and Research Engineer Godfrey Hounsfield, 60, of the British firm EMI Ltd., brooded over the same mathematical puzzle and independently reached the same solution. The puzzle: how to produce an X-ray image of tissue at any depth within a patient. The result: the CAT (for computerized axial tomography) scanner, a medical marvel now used in hospitals round the world. Last week the two scientists learned that they have something else in common: they will share the 1979 Nobel Prize in Physiology or Medicine and its accompanying cash award of $190,000.

The selection of the 1979 winners divided the house of Sweden's Karolinska Institute. The 15-member Nobel Selection Committee had sifted through nominees and sent a name or names to the full 54-member Nobel Assembly, but that choice was overturned after a lengthy debate. Though no rejected names were divulged, the schism was apparently an ideological one: some institute members insisted that winners be confined to scientists engaged in basic research, while others felt that achievements in medical technology should also be considered. The choice of the CAT-scanner pioneers seemed a perfect compromise. Their work with abstract physics and mathematics resulted in a lifesaving machine.

Cormack took the first step. A native of Johannesburg, South Africa, he became intrigued in 1956 by the difficulty doctors had in obtaining X-ray pictures of the brain. Because the cranium is so thick, they could make an X-ray beam "see" an abnormality only by injecting a patient with tracer dyes or air bubbles. When Cormack immigrated to the U.S. that year (he became an American citizen a decade later), he began exploring the physics of how X rays pass through differing body parts. Dividing this passage into cross-sectional slices, he found he could calculate the absorption of an X-ray beam by varying densities of tissue in any one of the slices. Cormack published his findings in 1963 but did not pursue a practical application of his idea.

Five years later, Hounsfield attacked the same puzzle for EMI, solved it in much the same way and applied it first to a prototype computerized head scanner, then to a body scanner, both of which EMI patented. These devices were able to distinguish soft tissues and organs and spot abnormalities by producing television images shaded according to the density of the tissue. Since then, widespread use of the scanner has drawn critics who argue that the machine's hefty price—up to $700,000 and more—drives up the cost of medical care at hospitals that could get by with cheaper methods. But the Nobel Committee declared: "No other method within X-ray diagnostics has led to such remarkable success in such a short time."