Scan Radiation - Check Out The Facts Beforehand
(Reuters Health) - Children
who suffer a head injury are often routinely examined by a CT
scan. Now, a Swedish team has found that radiation doses
typically delivered by such a scan during infancy may harm
intellectual capacity later in life.
While high doses
of radiation to the developing human brain are known to cause
mental retardation, it was not known if exposure to low doses
"has more subtle effects on cognitive function," Dr. Per Hall
from the Karolinska Institute in Stockholm and colleagues write
in this week's British Medical Journal.
they analyzed mental function and education in roughly 3000
18-to 19-year-old men who had been given relatively low doses of
radiation before the age of 18 months to treat a type of
birthmark called a cutaneous hemangioma.
classified the subjects into four radiation dose categories,
measured in milligrays (mGy): 1-20, 21-100, 101-250, and over
that the percentage of boys who attended high school decreased
with radiation doses greater than 100 mGy compared with the
lowest dose of 1-20 mGy. The proportion of high school attendees
decreased from roughly 32 percent among those with no exposure
to radiation, to 17 percent among those who received > 250 mGy.
Radiation of the
brain during infancy also had a negative effect on tests of
learning ability and logical reasoning but not on tests of
It is estimated
that a head CT scan performed on an infant imparts a radiation
dose of about 120 mGy.
the brain with dose levels overlapping those imparted by CT can,
in at least some instances, adversely affect intellectual
development," Hall and colleagues write.
Based on their
findings, they think that "the risks and benefits of CT scans in
minor head trauma need re-evaluating."
Medical Journal, January 3, 2004.