X-Rays: How Big A Risk To Kids? UF Researchers Seek Answers

March 18, 1998

GAINESVILLE --- A team of University of Florida researchers is trying to come up with definitive predictions of the risks to children from different types of X-ray exams, an area that often leaves worried parents with unanswered questions.

The project will measure radiation doses and calculate risks from such exams as general purpose X-ray exams; CT scans, which provide a three-dimensional picture of a part of the body; and fluoroscopy, used to obtain moving pictures of internal organs. Medical workers will be able to use the data to the pick the exam with the least risk as well as provide better information for parents faced with tough choices about children's care.

"If a parent said, `When my child was 1 or 2, she had a CT exam, some fluoroscopy and several chest x-rays, could you tell me what the actual dose was?,' no one can do that right now," said Kathleen Hintenlang, assistant radiation control officer at Shands hospital at UF and one of four researchers heading the project. "If the parent asks what the risk was, nobody can give a quantitative answer."

Hospitals routinely take measurements from X-ray machines to estimate the approximate size of the dose patients receive. Though all radiation carries some risk, the exams can be crucial to medical treatment -- indeed, they are lifesaving in some cases -- so the risk tends to be small by comparison.

But no one knows precisely how much radiation children absorb from different types of exams or if it increases their risk of developing cancer or leukemia later in life.

Hintenlang, who is researching the subject for her doctoral studies in environmental engineering, conceived the study after noticing premature and ailing newborns in the neonatal intensive care unit received more X-rays than other patients in critical wards.

Doctors give babies more X-rays because they often use medical devices such as catheters in treating the babies and because infants experience much more rapid internal changes than adults, said Jon Williams, chief of pediatric radiology at Shands.

Because children's cells divide rapidly as they grow, they are far more sensitive than adults to the chromosome-damaging effects of radiation. The increased frequency of exams piqued Hintenlang's curiosity, so she began researching the doses newborns were receiving.

She found information for adults, as well as for children in Europe, where treatment methods differ from the United States. To her surprise, however, no one had looked into the matter in this country since a 1979 study by the Food and Drug Administration. At the time, technical limitations prevented the FDA from measuring doses from fluoroscopy, and there also was no data on radiation doses to children from CT scans.

Assisted by today's faster computers and other technological advances, the researchers use a combination of physical and computer models of children to measure doses from different types of exams.

With a block-shaped head and body, the physical model of a 1-year-old child looks like a rough-hewn doll. But what counts is what it's made out of: a polyester resin mixed with chemical compounds to mimic soft organ, lung and bone tissue under an X-ray.

"They absorb X-rays just like the real tissues would," said David Hintenlang, Kathleen Hintenlang's husband and a professor in the nuclear and radiological engineering department and specialist in biomedical engineering and health physics.

The researchers subject the model to the same X-ray, fluoroscopy or CT machines used for pediatric patients at Shands. Tiny detectors implanted at places marked with felt-tip marker labels such as "liver," "bladder" or "stomach" measure doses to organs or tissues.

While the results are useful, they paint only part of the picture because the detectors measure the doses only at specific locations, said Wes Bolch, also a professor in the nuclear and radiological engineering department and specialist in biomedical engineering and health physics. The researchers will use complex computer models of children to generalize the measurements for the whole organs or tissues, he said.

The researchers applied for a $1.3 million grant from the National Institutes of Health but have already launched the project using $20,000 from the Children's Miracle Network.

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University of Florida

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