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A SYSTEM that uses sound waves to 鈥減rod鈥� suspect lumps deep within the body
could save millions of women from the trauma of a breast biopsy.

The hope is that the technique, under development at Duke University in
Durham, North Carolina, will use ultrasound waves to distinguish malignant
tumours from benign ones by measuring their elasticity.

Currently, suspect lumps are found using X-ray mammograms, ultrasound or
through physical examination鈥攂ut these methods can only locate the growth.
The only way to be sure whether it鈥檚 malignant or not is to perform a
biopsy鈥攕urgically removing part of the lump. 鈥淚n the US, the percentage of
biopsies that are performed on benign breast lesions is between 60 and 80 per
cent,鈥� explains Katherine Nightingale, head of the Duke team. Figures are
similar in Europe.

鈥淭here are no clinically available imaging methods that provide information
about the mechanical properties of tissue,鈥� says Nightingale. The Duke team uses
a hand-held ultrasound device to locate and measure the stiffness of lumps by
nudging them. 鈥淲e are finding that different tissue types respond differently,鈥�
Nightingale says. The team discovered that malign and benign lesions resist
prodding to very different degrees and recover their shape at different
speeds.

Their device intersperses conventional low-powered ultrasound bursts, used
for locating lumps, with much higher-powered 鈥減ushing鈥� beams
(see Graphic). The
higher pressure creates an acoustic force that moves the tissue very slightly,
typically between 10 and 15 micrometres.

The tissue stiffness is inversely proportional to the amount it moves, which
can be calculated using the ultrasound beams. 鈥淲e are investigating the
potential for using both of these parameters to differentiate benign from
malignant lesions,鈥� says Nightingale.

Their device could offer a quick and safe way to spot benign lumps without
surgery. And it can easily be added to existing ultrasound scanners used for
locating lumps. It鈥檚 safe, says Nightingale, because the high-power pushing
pulses last no longer than a millisecond and are only applied locally. This
prevents the tissue from getting hot.

鈥淚f it鈥檚 successful it would be a tremendous leap forward,鈥� says Stephen
Duffy at the Imperial Cancer Research Fund in London. 鈥淏ut you would want to be
absolutely sure that it didn鈥檛 miss malignant tumours.鈥� Biopsies are not as
uncomfortable as people think, he says, although it鈥檚 nicer not to have a needle
stuck in you.