CT in Kids: Balancing Risks, Benefits

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Between 1995 and 2008, the number of pediatric visits to an emergency department (ED) that included computed tomography (CT) increased fivefold, according to study results published online ahead of print by the journal Radiology. The researchers, led by David B. Larson, MD, MBA, Director of Quality Improvement in the Department of Radiology at Cincinnati Children's Hospital Medical Center in Ohio, say the substantial growth in CT use "is explained by increasing frequency of use, not by an increase in the number of pediatric visits to the ED."

Larson and colleagues also reported that about 90% of the visits associated with CT in children were made to nonpediatric-focused EDs (ie, those in which the average patient was older than 10). Given what is understood about the increased risks of radiation exposure in children, this finding raises additional questions and concerns about whether children received a radiation dose that was scaled to their body size or an adult dose. (The study was not designed to assess that.)

Whether to order CT in a child may be a daunting proposition for a clinician, particularly if he or she does not have subspecialty training in pediatrics. Ordering an unnecessary test may needlessly expose the patient to radiation, but missing a diagnosis that results in a negative outcome is also fraught with peril.

"This is the fine line that we walk in this conversation: On the one hand, CT uses radiation, so we should use it cautiously," Larson says. "On the other hand, the risk is very low, and we don't want to scare people out of getting CT."

Boom Years for CT Use
The National Cancer Institute reports that four to seven million CT exams are performed in children annually in the US, and that the use of CT (in both adults and children) has increased significantly since 1980, growing at an estimated rate of 10% per year. Larson attributes much of the increase observed in his study—an annual growth rate of about 13%—to the fact that the technology "improved significantly" during the time period examined.

"This is a time when the technology moved from basically axial scanning to helical scanning, and also from single detector to multichannel detectors," he says. "So, that translates into a much faster scan and a much higher-resolution scan. This is especially important in children, because it means less sedation, and in the ED, it means you can come to a decision very quickly."

Another factor driving the increased use of CT has been the ready availability of the equipment. A decade ago, major hospitals might have had a scanner, but it was not necessarily located adjacent to, let alone within, the ED. Smaller facilities may not have had a scanner, period.

"The availability of CT has increased exponentially over the past 10 years, and it has been a very reliable diagnostic tool," says John J. Graykoski, MPAS, PA-C, President of the Society of Emergency Medicine PAs and ER PA Supervisor at Luther Midelfort Mayo Health System in Colfax, Wisconsin. "It has tremendously enhanced our ability to identify problems much earlier and with much greater accuracy than our old plain films could do."

Speed and accuracy are particularly valuable in the emergency department, where, in the words of Michael P. Poirier, MD, Associate Professor of Pediatrics, Eastern Virginia Medical School, and Fellowship Director, Division of Emergency Medicine, Children's Hospital of the King's Daughters, Norfolk, Virginia, "you have one chance to get it right."

That time pressure to make an accurate diagnosis, coupled with the ever-present fear of litigation if the wrong decision is made or a negative outcome occurs despite the clinician's best efforts, may lead to the ordering of a CT scan that is not truly necessary. The prevailing wisdom might be "It's better to rule out the worst-case scenario and have that reassurance than to take the chance of missing something."

The drawback to that philosophy is that CT uses radiation—more of it than the average x-ray. The effective dose of radiation in the average CT scan of the head is equivalent to approximately 100 x-rays and in the average abdominal CT scan, 400 x-rays. Granted, these doses are from scans that are unadjusted for body weight, and in theory children should be undergoing CT with reduced radiation exposure parameters. Whether they actually are, particularly at nonpediatric facilities, is unknown.

"We hope that at all facilities, whether they are pediatric-focused or not, the dose is being tailored to the patient's size," Larson says, "but we don't know. We know that it has [improved] at children's hospitals; that study just hasn't been done at non-children's hospitals. I think the concern is that right now, it's actually rather difficult to monitor that."

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