A study last week pointing to the alarming rise of CT scans of children in the emergency room was deemed "disturbing" by the press. But a new paper suggests that, at least in Australia, the growth of CT imaging among children is slowing down.

In the study published Tuesday in the Journal of Medical Imaging and Radiation Oncology, the researchers found that while imaging of children tripled over the past two decades, in recent years the growth rate slowed among older children and teens and declined among the youngest.

"Based on combined data from Medicare and a dedicated pediatric hospital, it appears that the rate of pediatric CT imaging growth has slowed in recent years and even demonstrates a reduction in some age brackets," wrote the authors, led by Zoe Brady, with RMIT University in Melbourne.
The study comes on the heels of a report last week that found children in the U.S. visiting the ER had five times more CT imaging than they did 13 years earlier, based on 2008 data.

For the current study, researchers examined data from Australia's national health insurance, called Medicare. However, because research suggests about a quarter of CT exams are not funded by Medicare, the researchers supplemented their data with claims from Royal Children's Hospital Melbourne, a 250-bed pediatric hospital in Victoria.

Looking at Medicare claims from 1994 to 2009, they found CT use grew on average 8.5 percent per year for the past 15 years. In the same period, population growth only averaged 1.4 percent.

But the growth rate among children was lower than the total. For CT services billed to Medicare, it was 4.5 percent average growth per year, and at the Royal Children's Hospital it was 5.6 percent. Combing the two sets of the data, the researchers hit on an average growth for CT imaging in children of 5.1 percent.

Still, CT imaging for children did triple over the past two decades. CT services for children aged 0 to 18 grew from 17,500 billed Medicare claims in 1986 to 58,200 claims in 2008. For the children's hospital studied, in 1986, 1,500 patients had CT scans; but by 2008, it was 3,600 patients.

However, the growth of CT imaging for children has begun to slow down. For instance, for a five-year-old, the average yearly change in the CT rate (billed to Medicare) from 1987-2008 rose 2.5 per 1,000 patients. But from 2004-2008, it fell 2.4 per 1,000 patients. For older children and teenagers, the rates didn't fall, but they grew more slowly. The 1987-2008 CT imaging rates (again, billed to Medicare) rose 6.8 per 1,000, but in 2004-2008 it slowed to 4.5 per 1,000.

"While it is encouraging that the imaging rate for children and young people is lower than that for adults, overall the imaging rate continues to increase," the researchers wrote. However, they noted that some of the increase might be "warranted because of improvements in the diagnostic power of CT."

The researchers also found that the majority of the CT imaging of children at Royal Children's in Melbourne -- around 65 percent -- was not billed to Medicare.

In the U.S., medical radiation accounts for about half of all ionizing radiation exposure, according to the study. And CT is believed to be responsible for half of that exposure, making it the highest man-made source of population exposure among Americans.

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