Every day, about 19,000 children in the United States get a CT scan, which carries a radiation level equivalent to 30 to 442 chest X-rays.
The booming use of the scans along with research showing their overuse and link to cancer has experts launching initiatives to ensure patients are exposed to the least amount of radiation possible. Particular concern has focused on the unique threats the tests pose to children.
A child's growing body is more sensitive to radiation. Organs can be needlessly exposed because of their closer proximity. Kids have a longer lifespan for cancer to develop from a damaged cell. And children are often scanned using adult dosing techniques.
"One size does not fit all," when it comes to testing children, said Dr. Steven Don, pediatric radiologist at St. Louis Children's Hospital. "Each child needs to be individualized. I don't think of children as 'little adults.' "
CT - computed tomography - sends ionizing radiation through the body to produce 3-D images of tissues and organs. The use of CT scans in the United States has skyrocketed more than three-fold since 1993 to about 70,000 million scans annually. About 10 percent involve children. The U.S. Centers for Disease Control and Prevention reported last month that high-tech diagnostic imaging, which includes CT scans, is used in 14 percent of all emergency room visits - four times as many as in 1996.
Their use of CT scans has soared because improved technology has resulted in more accurate, detailed images that can provide valuable and life-saving information in detecting disease and preventing unnecessary procedures. The tests are noninvasive, quick and painless.
They have also been considered safe, with a very small risk of developing cancer. Two studies published in December in the Archives of Internal Medicine, however, "make us question whether we have gotten carried away in our enthusiasm," wrote Dr. Rita Redberg, editor of the medical journal, in her commentary about the studies.
National Cancer Institute researchers found that CT scans done in 2007 could be related to 29,000 future cancers and 15,000 deaths. About 15 percent of the projected cancers were from scans performed on children under the age of 18.
In addition, the University of California at San Francisco researchers looked at the 11 most common type of CT scans and found radiation doses varied significantly within and across institutions, exposing patients to more risk than previously thought. For example, 1 in 270 women who had a coronary CT scan at the age of 40 will develop cancer from the scan, compared to 1 in 8,100 with a head CT scan. For 20-year-old patients, the risks almost doubled.
Other studies have shown that as much as a third of scans are repetitive or unnecessary. The latest involved children arriving at emergency rooms with head trauma -- 20 to 25 got CT scans who didn't need them, researchers found. Their mild symptoms did not indicate a serious injury.
Even before the recent findings, a nationwide group of radiologists, medical technologists and medical physicists known as the Alliance for Radiation Safety in Pediatric Imaging has worked to reduce exposure in children. The group's 2-year-old education campaign -- Image Gently -- alerts the medical community of the need to tailor radiation doses, use other tests such as MRI and ultrasound when possible and weigh risks against benefits. The dosing rule is: as low as reasonably achievable.
Children's hospitals are at the forefront of the efforts. Radiologists at St. Louis Children's and Cardinal Glennon Children's hospitals review all requests for CT scans to make sure an answer can't be reached with another test. They work with technicians in adjusting the radiation dose to the child's weight and scanning the smallest area possible, being sure to consider results from previous scans. The doctors also allow for images that are a bit fuzzy.
"The study may not be pretty, but it is enough to answer the question," said Dr. Atchawee Luisiri, the pediatric radiology director at Cardinal Glennon.
Challenges, however, remain, advocates say. Dose indicators vary among different vendors. Technicians performing the scans are challenged to keep up with rapidly changing technology and must decipher user manuals written by physicists.
The FDA is working to address the problem, prompted last year by an investigation into a California facility where more than 200 patients received eight times the expected level of radiation, causing hair loss and skin problems. The FDA is meeting with manufacturers and experts to develop safety controls.
Don likened the problem to pharmacies handing out different doses when filling the same prescription. But, he said, the medicine can be essential.
"The most important thing is to not scare people away from getting a study which they need, but to make sure they have an open dialogue with the pediatrician about why it's necessary," he said. "And when you get the exam, ask the technologist, 'What are you doing to make sure the imaging is done at the appropriate dose?' "
LIMITING EXPOSURE FROM CT SCANS
The Image Gently Campaign promotes the following strategies to minimize radiation exposure from CT scans:
Image only when there is a clear medical benefit.
Use the lowest amount of radiation for adequate imaging based on size of child.
Image only the indicated area.
Avoid multiple scans.
Use alternative tests such as ultrasound or MRI when possible.
For more information, visit imagegently.org