Image gently: Reducing radiation dose in pediatric computed tomography through collaboration

Over 7 million computed tomography (CT) scans are performed on children annually in the United States. The vast majority of these scans occur in adult-oriented hospitals. When a child receives a CT scan using adult protocols, the radiation dose may exceed that received by an adult by as much as threefold.1 As the elevated pediatric dose improves the image quality, there is nothing to alert the radiologic technologist and radiologist that the child's dose exceeds the acceptable adult dose levels. Most CT scanners display two radiation dose indices: CT dose index and dose length product (DLP) (the product of the and length of the patient scanned) at the end of the scan. These indices are based on an adult sized phantom. Furthermore, most scanners assume that the patient is an adult and estimate the and DLP for the pediatric patient accordingly. This underestimated dose gives healthcare personnel a false sense of security concerning pediatric dose levels. Children are not small adults; they are more sensitive to radiation2 and require careful dose reduction techniques. Exposure to x rays similar to the energy and dose levels from pediatric CT scans may increase the incidence of cancer during adulthood: Increases for breast, intracranial, and other solid tumors have been reported.3–6 Since the energy and type of radiation ( x rays) from CT scanners differs from that of the World War II atomic bombs (a mixture of photons and particles covering a large range of energies), these two radiation sources have vastly different linear energy transfers. However, the large sample size and elapsed time since the irradiation results in some of the best data we have to estimate risks. One study showed that exposure in utero and as a child (, ) is associated with an increased risk of fatal cancer as an adult.7 The National Academy of Science states:2 “The same radiation in the first year of life for boys produces three to four times the cancer risk as does exposure between the ages of 20 and 50. For girls, the increased risk is six to eight times.” Medical physicists often work with radiologists and technologists to reduce the radiation dose patients receive from diagnostic examinations, but more should be done. When an imaging exam is requested, referring physicians should work closely with radiologists to ensure that the most appropriate examination is selected. As always, the benefit to the patient must be balanced against potential risk. Collaboration among all stakeholders—referring physicians, radiologists, radiologic technologists, patients, medical physicists, equipment manufacturers, regulatory agencies, accrediting bodies, and third party payers—is the key to proper management of patient dose levels.8 The Alliance for Radiation Safety in Pediatric Imaging was founded in 2007 to raise awareness and to provide training and educational materials to all of the stakeholders listed above.9 The four founding members—Society for Pediatric Radiology, American Association of Physicists in Medicine, American College of Radiology, and the American Society of Radiologic Technologists—have been joined by 44 affiliate members representing more than 600,000 physicians, medical physicists, and technologists internationally. On January 22, 2008, the Alliance launched its website (www.imagegently.org) to introduce the Image Gently campaign. Guidance on radiation dose for radiologists, radiologic technologists, medical physicists, pediatricians, and parents is available. A downloadable worksheet is also available to help radiology personnel develop pediatric techniques (regardless of the CT scanner's model or age) that ensure pediatric radiation dose levels do not exceed the site's adult radiation dose levels. The worksheet requires a medical physicist to make measurements for the CT scanner. In August 2008, the Alliance held a summit meeting with the manufacturers of CT equipment to urge development of a system to display correct values for pediatric patients.1 The manufacturers agreed to obtain attenuation data on different size anthropomorphic pediatric phantoms and develop pediatric correction factors. The Alliance has formed a Pediatric CT Physics Work Group in conjunction with NEMA's Medical Imaging and Technology Alliance to manage this process. The Work Group met in December 2008 to build consensus within the medical physics community on this project. Once complete,10 attenuation correction factors as a function of patient size will be posted on the Image Gently website so radiologists and technologists, in consultation with their medical physicist, may make corrections to displayed values for pediatric patients. Recently, the Alliance expanded its coverage to include interventional fluoroscopy.11 In the future, the Alliance plans to address pediatric issues in other imaging areas: Computed/digital radiography, general fluoroscopy, and nuclear medicine. Medical physicists are key to the success of Image Gently. The Alliance asks each medical physicist to serve as your institution's resource on radiation management and bring the critical issue of pediatric radiation dose reduction to the attention of your radiology colleagues. Your local involvement in improving the understanding of CT dosimetry and in developing optimal pediatric protocols is essential. In return, you will enhance your knowledge about clinical CT scanning of children and increase your effectiveness through collaboration.