Tuning in to Breast Tumors

"Did I understand that you cooked my breast with microwaves?" the woman angrily asked Dr. Norman Sadowsky, chief radiologist at Boston's Faulkner Hospital. Sadowsky reassured her that he had not. Yet her concern is typical of the initial response to the hospital's breast-cancer detection program. To help in the all-important early discovery of a disease that has reached epidemic levels in the U.S. (90,000 cases a year), Faulkner radiologists are using microwaves to spot breast cancers.

Microwaves, though they are being employed for everything from sending telephone messages to cooking steaks, would seem to be a highly unlikely medical tool. Like other electromagnetic radiation--notably X rays--they damage tissue at high enough energies. But the Faulkner microwaves are perfectly safe. Reason: the radiation involved is emitted not by the detector, as in conventional breast X rays (mammography), but by the body itself.

The idea comes from M.I.T. Astrophysicist Alan Barrett, who decided that the same electronic wizardry that was enabling him to tune in to microwaves from free-floating molecules in interstellar space could have a down-to-earth application. If they were reduced in size, he reasoned, the sensitive antennas could even pick up the weak microwave (or heat) emissions from a tumor.

Because of its rapid rate of growth and increased blood supply, a tumor is hotter than normal tissue and hence gives off more radiant energy. Thermography, or heat scanning, concentrates on looking for infra-red radiation to find tumors. But such waves are rapidly absorbed by bodily tissue; thus tumors that lie any distance below the skin's surface cannot be readily picked up by infra-red sensors. By contrast, microwaves--which are much longer and more penetrating--can locate tumors up to 10 cm. (4 in.) below the surface.

Not much larger than a stethoscope and used somewhat like it, the little antenna built by Barrett and an M.I.T. colleague, Philip Myers, is placed against nine different sites on the breast and held at each for about 10 seconds. If one spot turns out to be significantly hotter than a comparable area on the other breast, the supervising radiologist is alerted and can make other checks for a tumor, including X rays.

About 70% accurate, the gadget is admittedly less precise than mammography (90%) and only on a par statistically with infra-red thermography. But since there is no radiation risk and no need for a skilled X-ray interpreter to make an initial judgment, Sadowsky points out, the microwave detector could at the very least be used for prescreening women--especially those under 35 who are ordinarily not encouraged to have mammograms unless they have a family history of breast cancer or symptoms of the disease.

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