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Are CT scans safe for kids?

A small child's fall or head injury can be alarming, especially if unconsciousness results. Sometimes a CT scan is needed to rule out a skull fracture or bleeding inside the brain.

But as reassuring as the high-tech answer may be, it could do harm in the long run. Researchers have found that low-dose radiation to the head before 18 months of age can impair a child's intellect _ and a CT scan uses high-dose radiation.

In a study of 3,094 men, researchers at the Karolinska Institute in Stockholmfound that the greater their exposure to radiation as babies, the more impaired their learning ability and logical reasoning. The researchers studied men who received low-dose radiation therapy (the standard from 1930 to 1959) to the head as children, and then looked at their school and test performance. The findings suggest that radiation may damage children's developing brains and that doctors considering CT scans for minor trauma should weigh the possible consequences.

Dr. Marvin D. Nelson Jr., a neuroradiologist and chief of radiology at Children's Hospital Los Angeles, said the study raises important questions about the long-term effects of radiation.

But he pointed out that these findings should be followed up with a study directly assessing the effects of CT radiation instead of various kinds of radiation _ beta rays, gamma rays, X-rays and radium-226 _ with which the Swedish youngsters were treated.

Because 95 percent of men ages 18 and 19 are tested before military service, researchers were able to track information about the education and cognitive test results of these former pediatric patients.

The researchers found that the proportion of boys who attended high school decreased in relation to increasing doses of ionizing radiation _ the kind that penetrates the body _ to the front and back of the brain. The more radiation they were exposed to, the more impaired their learning ability and logical reasoning. Spatial recognition was unaffected. Because the dosages overlap those of CT scans, the findings raise questions about the long-term developmental effects of CT scans, which increasingly are used to assess minor head injuries. Although researchers had only data about radiation exposure before the age of 18 months, they said the findings raised questions about exposure of young children in general.

But Nelson said the kinds of radiation used then were different from today's CT, and that there are differences in the way various forms of radiation are absorbed by the brain.

CT is the preferred test when a doctor suspects that a child has a brain injury, the signs of which are unequal eye pupil size, weakness or lack of movement in the extremities and abnormal reflexes or unconsciousness for several minutes.

If a CT is recommended, Nelson suggests the parents ask the doctor or X-ray technician "whether the CT facility is using the proper reduced-dose protocols for children based on the size of the child." He noted that many hospitals and medical facilities use radiation dosing guidelines for adults, which "deliver two to three times more radiation than is needed for a proper pediatric CT."

When evaluating possible skull fractures and bleeding inside the skull and within and around the brain, Nelson said no other test provides as much information as a CT scan.

"The benefits far outweigh the risks," Nelson said.

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