May 4, 2009
Small Patients, Small Doses — Reducing Radiation Exposure
By Beth W. Orenstein
Vol. 10 No. 9 P. 12
The Image Gently campaign is part of a growing effort to avoid unnecessary radiation exposure in children.
A report released in March by the National Council on Radiation Protection & Measurements found that the amount of radiation to which Americans are exposed is growing rapidly. The report found that radiation exposure increased sixfold from 1980 to 2006 and that a large part of the increase is from medical imaging, particularly CT scans.
The increase in exposure to ionizing radiation has been of growing concern in the medical community because it may result in long-term harm to patients, including the potential to increase the chances of developing cancer. The concern has been particularly keen for pediatric patients, who are at a higher risk due to their bodies’ greater sensitivity and a longer life span to manifest any changes.
The pediatric radiology community has taken the issue to heart. In January 2008, four societies, the Society for Pediatric Radiology, the American Society of Radiologic Technologists (ASRT), the ACR, and the American Association of Physicists in Medicine, launched the Image Gently campaign to raise awareness of the need to child-size radiation doses when performing medical scans. In its first year plus, the alliance has grown significantly, says Marilyn J. Goske, MD, of the Cincinnati Children’s Hospital Medical Center and chair of the Alliance for Radiation Safety in Pediatric Imaging, the organization that sponsors the Image Gently campaign.
“Thirty-five societies and organizations have joined the alliance,” Goske says. “All told, we probably represent well over 600,000 healthcare professionals, including our target—radiologists, radiologic technologists, medical physicists, and industry—working together to improve radiation protection for kids.”
Another sign of the campaign’s success, Goske says, is that the National Quality Forum named Image Gently’s goal of reducing unnecessary exposure to ionizing radiation in pediatric patients as one of the 34 best practices for 2009. “We’re really pleased about this, as it will help promote the practice through a variety of other quality and safety organizations outside of radiology and help propel this issue to national attention within hospitals,” she says.
The alliance also has expanded the target for its message beyond physicians, technologists, physicists, and the industry. In January, in conjunction with the American Academy of Pediatrics, it began distributing brochures for parents that alert them to the risks and benefits of using medical imaging modalities requiring ionizing radiation. The brochures, available online through the academy and the Image Gently Web site (www.imagegently.org), are free and meant to be downloaded for distribution in physicians’ offices. “Parents can read the information, which is presented in a balanced way, and then, if they still have questions, they can ask the appropriate medical professional at the time of their child’s scan,” Goske says.
The campaign is also promoting the “My Child’s Medical Imaging Record” card, which parents can use to record any scans their children have undergone.
Goske believes the campaign is helping change practices at many hospitals and imaging facilities. However, she says, “We know that we still have a ways to go.”
Part of the problem, Goske explains, is that radiation and radiation dose is a complex topic. “There is a medical side, an emotional side, and a radiation dose side to the performance of the scan,” she says. “The medical side is that the patient derives a very real benefit from an indicated CT scan. This lifesaving technology may indicate a disease process that answers the doctors’ and parents’ questions as to why the child is ill. The emotional side is that there is concern on the part of the parents about the unfamiliar procedure, including potential changes from the radiation needed to produce the images. Lastly, measuring radiation dose for the individual patient is highly complex and, at this time, can only be estimated, particularly for children, on a routine basis.”
The amount of what is called “technique” used at the time of a CT scan on a child varies with the manufacturer, the year the equipment was made, and a variety of technical factors. “You can’t assign a ‘standard estimated’ dose for children of widely variable size. Consider the difference in technique used for a 4-lb premature infant compared to the 200-lb football player,” Goske says.
The Image Gently campaign has posted CT technique protocols on its Web site as a starting point. The protocols provide a proportion of what the adult technique is for different age groups. “Each location can use these protocols as a guide,” Goske says. “We have given guidelines, but the best thing to do is to work with the medical physicist, the radiologist, and the technologist so that the image is satisfactory on that piece of equipment and the lowest possible dose is used.”
Keith J. Strauss, MSc, director of radiology physics and engineering at Children’s Hospital Boston, developed the campaign’s technique using child-size phantoms on multiple scanners. Strauss says anyone can easily reduce dose if he or she ignores image quality, but that comes with its own potential risk: “If one reduces image quality and a subtle finding is missed, all the dose is wasted.”
Strauss’ goal, and that of the campaign, is not simply reducing dose but using the appropriate dose for the requested study. “We call it ALARA—as low as reasonably achievable,” he says. “The purpose of the generic protocols is to ensure that the pediatric doses are not greater than adult values. Because the pediatric patient is smaller in size than the adult patient, when an adult technique is used on a small pediatric patient, it can result in a dose that’s up to three times greater than the adult dose. If we can get every hospital in the world adjusting its protocols so that its pediatric patients don’t receive a dose that is greater than what adults receive, then we’ve reduced pediatric doses by up to a factor of three.”
Radiology departments with a variety of pediatric scanning frequencies seem interested in the guidelines, Goske says. “The universal protocols have been downloaded thousands of times, and the worksheet that goes with them has too. We have some indicators that suggest strongly that people are making changes and really embracing this,” she says.
Goske says that participating in the Image Gently campaign requires “some commitment on the part of the individual practice. Every practice has a medical physicist that it works with. Most don’t have them on site, but if the next time when the physicist comes out to calibrate their equipment they should say to him, ‘Look, we’re hearing about this need to reduce ionizing radiation in pediatric patients, and we want to child-size our practice; here’s the Web site, it’s pretty straightforward.”
Pediatric medical imagers say that child-sizing their CT settings are not the only steps they are taking to reduce exposure to ionizing radiation for their patients.
Greg Morrison, MA, RT(R), CNMT, CAE, chief operating officer for the ASRT and a leader in the Image Gently campaign, says that sometimes, physicians and technologists question the need for the x-ray or CT exam in the first place. “Sometimes, the referring physician orders a multiphased CT,” Morrison says. “But when the patient comes down for the study, based on the clinical history and potential diagnosis that they’re looking for, CTs with and without contrast may not be warranted. The technologists need to make sure they are alerting the radiologists to that fact, so that they can have some type of conversation with the referring physicians so that only the most appropriate exams are ordered.”
Marguerite T. Parisi, MD, MSEd, a pediatric radiologist and the section head of PET/CT at Seattle Children’s Hospital, says it is standard protocol at her hospital to review requests for CT and determine a study’s appropriateness. “If alternative modalities that do not use ionizing radiation, like ultrasound or magnetic resonance, can provide the necessary information to answer the clinical question, then we will perform that procedure instead,” she says.
Newer CT technology is also enabling imagers to lower the radiation dose in all patients, says Victor Ghioni, RT(R)(CT)(MRI), a CT technologist at Seattle Children’s Hospital who works with Parisi. The rotation times in newer equipment are faster, and there is more coverage per rotation, reducing the risks of repeat exposure due to motion, he says. “You can modulate the dose over a patient, and that ability is reducing radiation exposure even more. Newer technology is definitely enhancing the ability for us to reduce radiation dose to children,” he says. “It is also our responsibility as technical staff to understand those parameters that affect patient dose and image quality and adjust appropriately.”
At Seattle Children’s, Parisi says, “We are continuously updating our protocols and trying to reduce dose while maintaining image quality, not only for CT but for other modalities, including PET/CT, where we have pioneered low-dose protocols.”
The Image Gently campaign started with a focus on CT, but the effort to reduce children’s exposure to ionizing radiation recently has expanded to include conventional nuclear medicine studies, PET, and PET/CT. Last summer, S. Ted Treves, MD, chief of the division of nuclear medicine at Children’s Hospital Boston and a professor of radiology at Harvard Medical School, raised the question of lowering radiopharmaceutical dose for pediatric patients when he published a study in the Journal of Nuclear Medicine in June 2008.
Treves says he was alerted to the lack of universally applied standards for administering radiopharmaceutical doses to children undergoing nuclear medicine examinations when he was asked to participate in a multicenter study using one radiopharmaceutical as an endpoint. “For us to comply with the multicenter study, the doses of radiopharmaceutical they were recommending were significantly higher than what we use in practice here,” he says. “So I started a conversation with the directors of the trial and suggested to them that we would like to participate but not at the expense of giving the children a much higher radiation dose, since our practice shows that a much lower radiation dose is as effective.” The researchers eventually allowed Treves to use the lower doses for the study. He then decided to survey the 16 top pediatric hospitals in the country and ask them what their protocols were.
He found a great deal of variation in dose among the 13 children’s hospitals that responded to his survey. But Treves was not surprised by the finding, as the majority of radiopharmaceutical package inserts do not provide guidance on pediatric doses. When imaging children, he says, physicians typically base dosages on the patients’ body weight, the nature and type of the problem being investigated, the equipment being used, and their own experience. “This has led to the variations in dosage that currently exist,” he says.
Because no standards exist, Treves says, pediatric patients undergoing nuclear medicine exams may be getting doses that are too small to produce adequate results or high doses that do not result in improved diagnostic accuracy. Pediatric patients undergo fewer nuclear medicine exams than x-ray or CT exams and, when they do, the risk from exposure to small amounts of radiation is very low. Still, Treves says, the need to reach a consensus on pediatric-administered doses is great. “High doses that don’t result in improved diagnostic accuracy or low doses that do not permit adequate examination should both be considered unnecessary radiation exposure,” he says. “That is why it is critical that pediatric radiopharmaceutical doses be determined by the minimal amount necessary to ensure satisfactory examinations.”
Members of the Pediatric Imaging Council and the Society for Pediatric Radiology who practice nuclear medicine are examining administered dosages and are planning to formulate recommended pharmaceutical dosages within the year. Treves says that new image-processing techniques that have emerged in the last few years should make it possible to provide diagnostic information while lowering administered radiopharmaceutical doses.
Goske says that many individuals and groups have contributed to the Image Gently campaign to raise awareness and promote radiation protection for children. “This is a grassroots, voluntary effort,” she says. “Each organization and every radiologist, radiologic technologist, medical physicist, and CT manufacturer that has changed its protocols and lowered dose for children are the real measures of success of this campaign.”
— Beth W. Orenstein is a freelance medical writer and a regular contributor to Radiology Today. She writes from her home in Northampton, Pa.