NEWS TIPS FROM THE 2009 ANNUAL MEETING OF THE PEDIATRIC ACADEMIC SOCIETIES, MAY 2-5, BALTIMORE

Children with traumatic injuries get relatively high doses of radiation from imaging tests like CT scans and X-rays during evaluation in the emergency room and in the hospital, according to research from the Johns Hopkins Children's Center. Radiation exposure is a known risk factor for cancer later in life, and children are believed to be more vulnerable to the effects of radiation because their tissues are still developing and their cells dividing more rapidly than those of adults, the scientists say.

The average radiation dose received by children in the study was nearly 13 mSv, for millisievert (a unit for radiation exposure), and the highest dose was 75 mSv. By comparison, the average American is exposed to 3 mSv per year from environmental sources, researchers say. And while a safe threshold for radiation exposure has not been defined, cancer risk is believed to go up in proportion to the amount of radiation received, with every single exposure causing a corresponding rise in cancer risk, according to a 2005 landmark report by the National Academy of Sciences.

Combing through a year's worth of medical records, researchers studied the charts of 945 patients treated at Johns Hopkins Children's for traumatic injuries, calculating the cumulative radiation dose for each patient by adding all the imaging tests the patient underwent at the ER and/or the hospital, if subsequently admitted.

Patients who were admitted to the hospital after being brought to the ED, and had repeated radiological tests, had a higher average radiation exposure at 18 mSv, compared to an average of 8mSv for those who were evaluated in the ED and sent home. Burn patients had the lowest exposure (1 mSv on average), while those injured in car accidents had the highest exposure, 18 mSv.

On average, children had four to six imaging tests that exposed them to radiation, including X-rays, CT scans and fluoroscopy (a real-time X-ray used during certain surgeries). CT scans, which provide the most detailed three-dimensional images, carried the highest radiation exposure, followed by fluoroscopy and traditional X-rays.

The Johns Hopkins team warns against unnecessary anxiety over too much radiation exposure from medical tests, but says trauma teams caring for these children must carefully weigh the benefits of quick diagnosis against the risk of too much radiation from multiple or repeated tests, especially if their diagnostic value is uncertain.

"In a trauma case, treatment decisions must be made in minutes, even seconds, and a CT scan can give a doctor invaluable information that could mean the difference between life and death," says lead investigator Marissa Brunetti, M.D., a critical care specialist at Johns Hopkins Children's. "But all we're saying here is, use CT scans and other radiation imaging tests sparingly and only when absolutely necessary, not as a diagnostic crutch. Ask yourself: Is another option, such as an ultrasound or careful observation, available?"

Principal investigator of the study: Robert Brown, M.D., of Johns Hopkins. Other investigators include Mahadevappa Mahesh, Rosemary Nabaweesi, Susan Ziegfeld, and Paul Locke.