Ray of light for breast cancer scans

Breast-screening could in the future be done without X-rays using a technique that is as harmless as a reading lamp, a conference heard last month.

The screening harnesses rays that are just beyond the range of the human eye - near-infrared.

The technique depends on a discovery made 20 years ago that when near-infrared rays were shone through a cat's head, some of them passed through it and could be detected on the other side. The rays that did not get through the head had been absorbed by haemoglobin in the cat's blood. Because haemoglobin transports oxygen, scientists knew that the more infra-red that was absorbed, the more oxygen was present in that part of the brain.

David Delpy, professor of medical photonics at University College London, said that his team had decided to apply the method to the breast. They reasoned that as a tumour grows its blood supply also grows - which means that there is more oxygen circulating around it. The team, which includes Simon Arridge and Jeremy Hebden, thinks that a near infra-red breast scan will reveal tumours because of the extra oxygen that surrounds them.

The machine could detect tumours earlier than conventional X-rays, which depend on detecting tiny calcium deposits that take time to develop.

The team told the medical engineering conference, held at the Royal Academy of Engineering, that it hopes to have a machine built in about six months. Laboratory experiments have already shown that it would be able to detect to a resolution of five millimetres.

The scientists have just received a grant from the Wellcome Trust to develop a machine that can be used in trials. The screening would be less harmful than X-rays but would have poorer resolution. Professor Delpy said that the two methods should be used in tandem.