The research showed that 0.6 per cent of the 124,000 patients found to have cancer each year can attribute the disease to X-ray exposure. Diagnostic X-rays, which are used in conventional radiography and imaging techniques such as CT scans, are the largest man-made source of radiation exposure to the general population.

Although such X-rays provide great benefits, it is generally accepted that their use is associated with very small increases in cancer risk.

Amy Berrington de Gonzalez, who led the British study, said: “Because of the large number of people exposed to diagnostic X-rays every year, even a very small risk to an individual from each X-ray could result in some cases of cancer being caused by these investigations.”

The research, conducted by Oxford University and Cancer Research UK and published in The Lancet, used mathematical models to estimate the number of cancers caused in Britain and 14 other industrialised countries. The models were based on the number and type of diagnostic X-rays performed every year, and the doses delivered.

While the findings confirm previous research into the small but identifiable dangers posed by diagnostic X-rays, Britain had one of the lowest estimates of X-ray-associated cancer cases. Researchers said that the figure reflected the lower use of X-rays in Britain.

Dr Berrington de Gonzalez, of Cancer Research UK’s Cancer Epidemiology Unit at the Radcliffe Infirmary, Oxford, said that the risks may have been overestimated, but it was unlikely that they had been underestimated substantially.

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