to low doses of ionising radiation during childhood affects intellectual
capacity in later life, conclude researchers writing in
the British Medical Journal.
CT (computed tomography)
scanning, which delivers high doses of ionising radiation, is increasingly
being used in young children after minor head
trauma and is occasionally used in the diagnosis of epilepsy in children.
The study, based at the Karolinska
Institute in Stockholm, involved
3,094 men who had received radiation therapy before age 18 months during
1930-59. At age 18 or 19 years, their intellectual capacity was tested
and high school attendance was recorded.
The proportion of
boys who attended high school decreased with increasing doses of ionising
radiation to both the front and back parts of the brain. A significant dose-related response was also seen for learning ability
and logical reasoning, but not for spatial recognition.
The authors said
that intellectual development could be adversely affected when the
infant brain is exposed
radiation at doses equivalent to CT scans
of the skull.
The risk and benefits
of CT scans in minor head trauma need re-evaluating, the research