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SCALPELS fitted with probes that can instantly reveal whether cells are
cancerous may soon help surgeons operating on tumours. The technology, which can
detect the earliest stages of cancer, could even replace biopsies.

鈥淚t could be clinically very valuable, if the technology lives up to
expectations,鈥� says Ian Smith of the Royal Marsden Hospital in London.

The probes exploit a well-known trick of light known as the 鈥淩aman effect鈥�,
which is already used to analyse various materials, including diamonds. When
laser light bounces off a material, almost all the scattered light has the same
wavelength as the laser. But a very small fraction鈥攖he Raman
spectrum鈥攈as different wavelengths.

Different types of living tissue also have characteristic Raman spectra. 鈥淭he
Raman spectrum is a sort of optical fingerprint of the molecular composition of
the tissue,鈥� says Gerwin Puppels of the Erasmus Medical Centre in Rotterdam.

His team has developed a fibre-optic probe about a millimetre across. It
measures the Raman spectrum of a tissue and compares it with a database of other
spectra to see whether the tissue is cancerous.

To test the technique, Puppels鈥檚 team applied a carcinogen to rats鈥� palates.
Cells exposed to the carcinogen become cancerous over a period of weeks. The
first stage is called low-grade dysplasia (LGD). The second is high-grade
dysplasia (HGD), or localised cancer.

Raman spectra from the rats鈥� palates were compared with biopsies on the same
tissues. The team diagnosed HGD correctly every time, LGD in 7 out of 9 cases,
and healthy tissue in 17 of 19 samples. 鈥淲e can analyse the spectra to the point
that we can detect different stages of cancer development,鈥� says Puppels.

Anita Mahadevan-Jansen and her colleagues at Vanderbilt University in
Nashville, Tennessee, have also got good results with their own Raman
spectroscopy probes. Of 24 women who were undergoing standard examinations for
cervical cancer, the technique detected HGD correctly every time, she says.

The technology could one day guide or even replace surgical biopsies,
Mahadevan-Jansen says. 鈥淏iopsies are the gold standard, and initial studies show
that we are getting pretty close to that.鈥�

鈥淭o be able to guide the biopsy to an area of abnormality would be a very
useful advance,鈥� says Smith. It would also open up the possibility of instant
treatment.

Scalpels fitted with Raman probes could also help surgeons. In nearly 25 per
cent of operations to remove breast cancer, for instance, surgeons miss some
cancerous tissue and have to operate again, says Smith.

The next step is to make the probes faster. 鈥淲e are working towards
collecting and interpreting the signal in one second,鈥� says Puppels.