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Prevalence of Multiphase CT Scans Increases Pediatric Radiation Exposure

CT scans taken at nonpediatric imaging facilities more frequently use multiple phases and higher doses of radiation.

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Jill Sakai, Contributor
Fri, 08/24/2018

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Computed tomography images internal structures using ionizing radiation, which is of particular concern for pediatric patients, whose developing bodies may be more sensitive to damage or long-term effects. A recent study evaluated how the common practice of acquiring multiple CT scan phases may contribute to pediatric radiation exposure.

Members of the radiology team at Children’s Healthcare of Atlanta noted that many patients referred to their facility had received prior evaluation with multiphase CT scans. They conducted a retrospective analysis of 754 contrast-enhanced abdominal-pelvic CT scans of children taken at external facilities between 2012 and 2015 and 939 scans taken at their own facility between 2013 and 2015. They evaluated the number of scan phases used and, where possible, estimated radiation levels received by the patients.

Many of the external scans “had significantly higher radiation doses than what we use to appropriately diagnose conditions when we perform abdominal CT,” said study co-author Sarah Sarvis Milla, a pediatric radiologist at Children’s Healthcare of Atlanta. But, she adds, the largest contributor to increased radiation exposure was the use of multiphase acquisition.

More than half (55 percent) of the evaluated CT scans performed by external facilities used at least two phases, and 2 percent used three or more phases. By contrast, only 12 percent of the scans at Children’s Healthcare of Atlanta were multiphase.

Appropriate use criteria published by the American College of Radiologists state that multiple phases should not be used in routine CT scans for either adult or pediatric patients. The analysis excluded outside facility scans for which clinical indications potentially justified the use of additional phases.

For scans with available dose data, radiation dose per scan was more than twice as high at external facilities, the researchers found. Patients younger than 6 years had the largest difference, with exposure estimates nearly three times as high at outside facilities, even after accounting for body size. Overall, this means that a two-phase scan at one of the external imaging facilities may have used four to six times as much radiation as a single-phase study at their center, the investigators report.

The team published its findings online in July in Pediatric Radiology.

Providers less familiar with pediatric imaging may default to a scan type that seems to offer more information, even at the cost of additional exposure, said Jonathan Swanson, a pediatric radiologist at Seattle Children’s Hospital who was not involved in the study. But “in truth, the knowledge you gain with those additional phases is minimal and often doesn't help that much,” he said.

The prevalence of multiphase scans reported in the study is higher than what Swanson sees in his own practice. “But I do think, in my experience, that it is not uncommon for adult-based hospitals, community hospitals,” he said. “They're more likely to do a multiphase [scan].”

The authors note that pediatric centers may have more incentive and resources to devote to optimizing protocols for children. However, they recommend that eliminating routine use of multiple phases is attainable for all facilities and would have a large impact on pediatric radiation exposure.

“It takes quite a bit of time and effort to optimize doses on CT scanners and optimize protocols. It's not as simple as just turning a switch down to a lower setting,” said co-author Bradley Rostad, also a pediatric radiologist at Children’s Healthcare of Atlanta. But, he noted, “a simple, easy, first step is just to eliminate that extra phase, which doesn't require additional optimization.”

Overall, Swanson suggests a need for better communication among all parties involved, including parents asking questions on their children’s behalf, radiologists discussing options with ordering physicians, and the medical community making efforts to improve awareness of the issue, such as through the Image Gently educational campaign.

“We need to do a better job of reaching out to ordering physicians, both at the family practice level and at the pediatric level, and preach why we think you don't need to do multiphase,” Swanson said. “I can do that here in a children's hospital, but this data shows it's not so much what's happening in the children's hospital -- it's happening in the community.”

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