Photon opportunity

A breakthrough in laser technology could provide the key to developing cheap and fast diagnosis of certain cancers.

Tumours in the digestive tract and gullet can be hard to discover, as it is difficult to obtain a tissue sample from these areas.

Biopsies cause bleeding and irritation and even risk perforating the vessel wall, while testing removed tissues and interpreting the results is a slow, highly-skilled and subjective process as pathologists must base their diagnosis on the shape and appearance of the cells.

But research by metrology specialist Renishaw reveals that Raman spectroscopy could improve diagnosis. The technique – which has been used to examine diamond-like coatings on computer hard drives for almost a decade – could allow medical specialists to classify pre-cancerous tissue, according to findings presented at last week’s Photon 02 optics and photonics conference in Cardiff.

Renishaw, in conjunction with the Royal Gloucester Hospital and Medlink, has been investigating the possibility of developing a fast diagnostic technique using light applied to either a prepared biopsy, or during an endoscopy, removing the need to take samples. Raman spectroscopy involves touching areas of tissue around a point with a light-emitting probe that sends photons into tissue and measures the amount of light returning.

Molecules of different substances vibrate at different rates, and this vibration causes a characteristic frequency shift in the light. An analysis of the frequency shifts should give a molecular fingerprint of the tissue, showing its biochemical make-up and removing the pathologist’s subjective judgment from the process.

According to the Office of National Statistics, around 18% of malignant tumours in adults are found in the gastrointestinal tract, and oesophageal cancer has increased by more than 45 per cent over the past 20 years. However, developing a cost-effective screening process has been hard.

‘Around 90% of biopsy samples are normal tissue, and each patient can have about 20 taken,’ said Dr Bob Bennett, business manager for Renishaw’s Spectroscopy Products Division.

However, the team still has several problems to overcome. ‘The technology is difficult to develop because of the problem of getting the probe down a small hole,’ said Bennett. ‘Signals are also much weaker in vitro, and while studies are still largely academic we feel the area is worth looking at. We have had some very good results in laboratory tests.’

Note: Researchers at Birmingham University have been using the Rutherford Appleton Laboratory’s versatile laser-plasma X-ray source to carry out radiation experiments on cell samples.

The team hopes to discover more about the relationship between cells to find out why destroying one leads to the death of its neighbours, as occurs during cancer radiotherapy.

The Central Laser Facility equipment can fire photons from numerous angles and at various speeds, and can produce soft X-rays. These can be concentrated into narrow lines 25 microns wide, with a sharp edge. They do not penetrate the tissue to a great depth and can be focused on a single cell without straying into and harming its neighbours.

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