Computerized tomography (CT) scanning involves taking X-rays from a rotating camera and feeding the results to a powerful computer to create cross-sectional views of organs in the body. The procedure—simple and painless, taking less than 10 minutes—allows doctors to detect injuries and diseases that don’t show up on standard X-rays. CT scans save countless lives and prevent many misdiagnoses and unnecessary surgeries. Given CT’s advantages, it’s no surprise that its use has surged in the last two decades.

But the technology’s diagnostic power carries a cost: a CT scan can expose a patient to 100 to 500 times the amount of radiation she would get in an X-ray, increasing her risk for cancer. Fortunately, that picture may be changing, especially for children, whose smaller, rapidly growing bodies make them even more susceptible than adults to radiation-induced cancer. In data compiled by the American College of Radiology’s Dose Index Registry, which tracks and categorizes the radiation given by CT scanners in U.S. hospitals, Yale-New Haven Children’s Hospital (YNHCH) recorded the lowest doses of any academic hospital in the country in many age groups and types of pediatric radiation.

“The numbers are very impressive,” says T. Rob Goodman, M.B., B.Chir., interim chair and professor of diagnostic radiology and chief of pediatric diagnostic imaging at YNHCH. “We’ve more than halved the number of CT scans done on children despite more than doubling the number of scanners in the hospital.” In 2003 Yale-New Haven Hospital had three CT scanners and performed 4,844 CT scans on children. In 2012, with seven scanners, the hospital performed 2,344.

The lower numbers are partly due to a greater awareness among physicians of CT’s risks. Says Lei Chen, M.D., associate professor of pediatrics, “We have really started thinking critically about the risks and benefits of CT scans. We often elect alternative strategies, either watchful waiting—in cases of suspected head trauma—or ultrasound and MRI [magnetic resonance imaging].”

In January 2008, the Alliance for Radiation Safety in Pediatric Imaging launched a campaign to educate doctors and the public about cumulative radiation exposure. Manufacturers began building scanners that automatically adjusted doses based on a patient’s age and weight and the sensitivity of the area to be scanned.

Goodman became concerned about CT scan radiation even earlier, in 2003, when he left Oxford University to join the School of Medicine’s faculty and realized that Americans were receiving three times more medical radiation than Europeans. He began conducting grand rounds for pediatricians on reducing radiation doses, and urged them to consider alternatives to CT scans such as ultrasound. He worked with YNHCH’s medical physICISts to adjust CT scanning practices to give children the least possible dose while still making images useful for diagnosis.

Not all imaging centers have changed their approach. A study published in June in the journal JAMA Pediatrics reported that of the estimated 4 million CT scans given every year to U.S. children under age 15, a third are unnecessary and may lead to 5,000 cases of cancer.

Still, doctors say that in some cases a CT scan is the best test. “If we can get the necessary information from a plain X-ray or an MRI, we forego the CT scan,” says Cordelia W. Carter, M.D., assistant professor of orthopaedics and rehabilitation. However, for certain fracture patterns, such as a common ankle “triplane” fracture, a CT scan provides the amount of detail a surgeon needs. Still, Carter adds, “we are very aware of the increased radiation associated with CT scans, and we do whatever we can to minimize the patient’s exposure.”

Goodman expects the use of CT to drop further as MRI, which emits no radiation, becomes the standard tool for many diagnoses. His campaign to lower radiation doses at YNHCH has been so successful that he now sometimes finds himself urging clinicians and parents not to avoid CT in the correct clinical setting.

“If the suspicion is high that a child may have a significant lesion in the lung,” says Goodman, “parents should be reassured that the CT radiation doses at Yale are the lowest in the country and doing the scan is what’s best for the patient.”