Dr. John is a Professor of Radiology and Pediatrics, Department of Radiology, University of Texas Houston Medical School, and Chief of Pediatric Radiology, Memorial Hermann Children's Hospital, and Chief of Diagnostic Radiology, Memorial Hermann Hospital, Houston, TX.

It is a familiar scene in medicine: the thrill of discovering new, more elegant ways to diagnose and treat disease, followed by the recognition that the new capabilities are accompanied by the potential for harm. Radiologists understand that the responsibility for monitoring and controlling radiation exposure to patients is a primary role of the specialty and have long attended to that task with minimal fanfare. In our enthusiasm for developing more accurate and sophisticated diagnostic imaging techniques, however, patient safety may be relegated to a secondary consideration. This is especially true for pediatric patients, who are physiologically different from adults and comprise a relatively small proportion of the patient population in many radiology practices.

Earlier this year, the association of radiation-induced cancer with radiation exposure to children undergoing diagnostic computed tomography (CT) captured the attention of the public, due to several important publications on this issue ^1,2 and a sudden blitz of dramatic media coverage. The negative publicity had the positive effect of raising awareness within the medical community about the potential for high radiation exposure to patients undergoing helical CT. Medicine responded with a call for renewed commitment to finding ways to better manage this safety issue.

Recently, the Society of Pediatric Radiology sponsored a conference addressing the concept of ALARA (As Low As Reasonably Allowable) in CT of pediatric patients. Participants included a diverse constellation of professionals, including radiologists, radiobiologists, technologists, physicists, engineers, oncologists, vendors, and government officials. Many of the speakers were leaders in science and medicine with long-standing experience in the effects of radiation and radiation control. The conference provided an exceptional opportunity for communication and discussion of what is already known about the issue and for brainstorming about available remedies and areas where future research is needed.

Although many questions and controversies remain regarding radiation and cancer in children, consensus is evident on several points. The increased risk of radiation-induced cancer in children caused by exposure during CT remains very small for any given patient, and the benefits for most indications are relatively large. Nevertheless, the overall risks to children of this country become significant when multiplied by the large number of studies performed, estimated to be more than 2.5 million exams per year and growing. Research on A-bomb survivors who received lower doses of radiation exposure now provide risks estimates for radiation-induced cancer in the population exposed to doses similar to those occurring with CT. Children are 10 times more sensitive to radiation-induced cancer than adults, presumably because of the presence of a larger number of actively producing cells in infants and children. Studies of fetal exposures due to in utero radiographs suggest that risk of cancer increases with a dose of approximately 1 rad to the fetus. If radiographic techniques are not reduced properly for children, the dose to individual organs is much larger in infants and children than in adults, and the close proximity of the organs in a smaller body makes scatter more important. Radiation doses can be decreased significantly by simple adjustments of the imaging parameters during CT.

All participants of the conference agreed that action is needed urgently to ensure the safety of children undergoing CT, and many helpful ideas were proposed. Several of the large children's hospitals have already implemented creative and successful programs to decrease radiation dose during CT. One of the articles in this issue of Applied Radiology presents one institution's experience with improving CT in children, including radiation exposure. Many radiology practices in the United States face special challenges in establishing effective low-dose CT policies, because children are seen much less commonly than adults. The answer to the challenges involves awareness, education, and constant vigilance on the part of all who are involved in pediatric imaging. Radiologists must impress upon the manufacturers and designers of imaging equipment the importance of making it easier to monitor and limit exposure to radiation and other potentially harmful by-products of imaging modalities. Technologists must be educated about the importance of minimizing radiation dose in pediatric patients and should be involved actively in planning strategies for decreasing exposure to children during CT. Physicians referring children for CT must be counseled about safer imaging alternatives when appropriate. The primary responsibility lies with the radiologist to ensure that infants and children receive the minimum necessary dose of radiation to provide the information needed from CT.

The recent surge of interest in radiation exposure during CT provides an excellent opportunity to examine potentially harmful effects of other common forms of imaging in pediatric patients. Although modalities such as ultrasound and magnetic resonance imaging are considered safer than those that use ionizing radiation, the energies used for these imaging modalities can also have undesired effects. The American Institute of Ultrasound in Medicine has published guidelines for the safe use of diagnostic ultrasound, which can have potentially harmful thermal and mechanical effects on fetal tissues and in the brain and gastrointestinal tract of infants. Recent reports of accidents in magnetic resonance scanners due to flying metal projectiles reminds us of the need for constant surveillance of personnel and patients near strong magnetic fields. All of these technologies provide unquestioned benefits to the health of children, but our responsibility for protecting these young patients from harm during imaging endures. Vigilance pays.