Young toddlers may be most at risk

Researchers in Sweden say they have uncovered evidence that the scans may damage toddlers' brains.

Their study of more than 3,000 men who had scans before they were 18 months old found many went on to develop learning problems.

Writing in the British Medical Journal, the researchers called for new guidelines to warn doctors of the risk.

CT or computed tomography scans use ionising radiation to take pictures of the inside of the body. They are more detailed than conventional X-rays.

The risk and benefits of computed tomography scans in minor head trauma need re-evaluating Dr Per Hall

They are used on patients with a wide range of suspected problems, from cancer to suspected brain injuries.

In recent years, doctors have started to use CT scans on young infants.

Previous studies have suggested that high doses of ionising radiation can damage the developing human brain.

Radiation therapy

Dr Per Hall and colleagues at the Karolinska Institute in Stockholm decided to carry out research to see if low doses of ionising radiation have a similar effect.

The researchers identified 3,094 men who had received radiation therapy as toddlers between 1930 and 1959.

They also obtained information on the intellectual capacity and school record of each of these men.

They found that the higher the dose of radiation the more likely these men were to suffer learning problems later in life.

They were also more likely to have dropped out of school.

The researchers suggested new guidelines are needed to ensure doctors do not use CT scans on young infants.

"The risk and benefits of computed tomography scans in minor head trauma need re-evaluating," they wrote.