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CT scans are an important diagnostic tool when used appropriately

June 7, 2012


The American Association of Physicists in Medicine (AAPM) encourages parents to discuss the need for any diagnostic medical procedures for their children with their physician. AAPM believes parents may have additional questions regarding computed tomography (CT) scans for their children in light of the results of a study (Pearce et al.) published on line June 7, 2012 in the Lancet regarding radiation risk from pediatric CT. Specifically, besides consideration of medical appropriateness, parents may request information regarding steps being taken to keep radiation doses as low as possible while ensuring that the exam is of sufficient quality to yield the correct diagnosis. A number of important and ongoing initiatives are helping to ensure that the appropriate dose is used in medical imaging. The AAPM believes that communication to parents of these important initiatives may assist in reassuring parents that the entire medical imaging community is working diligently to keep CT imaging a safe and effective diagnostic tool. Some of these initiatives include:

  1. Image Gently®AAPM is a founding member of the Alliance for Radiation Safety in Pediatric Imaging along with the Society for Pediatric Radiology (SPR), the American College of Radiology (ACR) and the American Society of Radiologic Technologists (ASRT). Image Gently educates providers on opportunities to lower radiation dose used in the imaging of children. The campaign, started in Jan. 2008, now includes 70 Medical Organizations Worldwide. AAPM encourages parents to read the “letter to parents” developed by the Alliance.

  2. Image Wisely®AAPM, along with the Radiological Society of North America (RSNA), ACR and ASRT co-founded the initiative to educate physicians on opportunities to lower dose and ensure appropriate imaging. The initiative also provides patient education materials, including a patient medical imaging record card developed with the FDA.

  3. Standardization of CT Nomenclature and Protocols: AAPM has led the effort to produce and make freely available a set of reasonable scan protocols for frequently performed CT examinations, summarizing the basic requirements of the exam and giving several model-specific examples of scan and reconstruction parameters. This work is being performed by a multidisciplinary group that includes academic and consulting medical physicists who specialize in CT imaging, representatives of each of the major CT scanner manufacturers, and liaisons to the American College of Radiology, American Society of Radiology Technologists, and the U.S. Food and Drug Administration (FDA). Two such protocols can be found on the AAPM website. A pediatric head protocol is currently under development, as are adult and pediatric protocols for CT imaging of the chest, abdomen and pelvis.

The Lancet Study

In the recent paper by Pearce et al, the authors noted an apparent increase in brain cancer and leukemia as the estimated patient radiation dose increased to levels similar to several CT exams. Two points are critical to keep in mind when considering this study.

First, the baseline risks for these cancers in the age ranges studied are very low. Tripling a small absolute risk still results in a small absolute risk. For example, they note that in the ten years following a head CT scan of 10,000 children performed in their first decade of life, one excess brain tumor and one excess case of leukemia might occur. This extremely small risk is easily justified by the immediate benefit to the patient of a medically appropriate CT scan. For example, in head CT obtained for trauma, an injury is detected in at least 1 in 50 children. CT is an extremely fast and accurate diagnostic test that does not require anesthesia or sedation in young patients, which are associated with a small risk to the patient.

Second, the doses assigned to patients in the study were estimated from national surveys and were not actual doses measured in any given patient. These doses were consistent with typical doses used over a decade ago, using older scanner technology and a “one-size fits all” approach to setting scan parameters; they are likely 2 to 5 times higher than doses currently used on typical CT equipment. The newest CT technology offers additional dose reduction to patients through the use of customized scan settings and advanced scan and reconstruction techniques.

Action Needed

AAPM urges Congressional action in the following areas to ensure appropriate imaging and lower the radiation dose that Americans receive from scans each year by:

Conclusion

AAPM believes that patient safety in the use of medical radiation will be increased through consistent education and certification of medical team members, whose qualifications are recognized nationally and who follow consensus practice guidelines that meet established national accrediting standards. The expertise of AAPM members in medical imaging technology, performance optimization, and radiation safety is an important component of these national efforts to ensure safe and appropriate medical imaging.

To arrange an interview with an AAPM spokesperson, please contact Lisa Rose Sullivan at 301-209-3387 or lrose@aapm.org.