MAMMOGRAMS reveal lumps in breasts but only a painful biopsy can prove if a lump is benign or cancerous. Now, however, a new device from the US could avoid the need for many biopsies.
Approved for use by the Food and Drug Administration last week, the T-Scan 2000 from TransScan Medical of Ramsey, New Jersey, detects tumours by passing a tiny electric current through the body and measuring the differences in resistance between normal and tumour tissue.
"We want to use the T-Scan to prove there is no cancer. What we're saying is: do the biopsy to prove there is disease," says George Solomon, chief executive officer of TransScan. The results of a mammogram-a low-dose X-ray-are often difficult to interpret. To be safe, doctors perform biopsies, removing tissue from the breast to see if it is cancerous.
Every year in the US, 25 million women have mammograms and about 800 000 have biopsies after results reveal suspect tissue. But only 180 000 actually have breast cancer. TransScan claims the T-Scan could find 6000 cases of cancer that would otherwise go undetected, and spare more than 600 000 women the pain of a biopsy.
The device consists of a hand-held probe that contains a small matrix of sensing electrodes. This is gently placed on the breast above the suspect region, and a wire is attached to the patient's hand to complete the circuit. An alternating current of 1 volt is then passed through the body.
Differences in structure between tumour tissue and normal tissue make tumours about 40 times more conductive than regular tissue. The probes detect these differences as the device is passed over the breast, and a computer generates an image that can then be interpreted by a technician.
"The T-Scan device has the potential to reduce the number of negative biopsies, thus saving women worry about breast lesions that turn out to be noncancerous. It also has the potential to increase the identification of women who should be referred for early biopsy," the FDA said.
Other researchers are working on related techniques. The National Institutes of Health near Washington DC is developing an instrument that maps conductivity variations by passing an oscillating current through the body in a strong magnetic field, which creates detectable ultrasonic vibrations (This Week, 16 January 1999, p 9).
Author: Kurt Kleiner, Washington DC
New Scientist issue 1 May 1999
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