While the FDA launched an initiative to reduce unnecessary radiation from medical imaging, the agency lacks the authority to truly track and regulate CT scanning without the legal support of a congressional act, Rebecca Smith-Bindman, MD, said in an interview and wrote in a perspective in the June 23 issue of the New England Journal of Medicine ( NEJM).
“Notably absent from the initiative are plans to standardize, monitor or regulate how imaging equipment is used,” said Smith-Bindman, from the departments of radiology and biomedical imaging at the University of California San Francisco and a visiting research scientist in the radiation epidemiology branch at the National Cancer Institute in Bethesda, Md.
She compared the state of CT imaging today to the state of mammography prior to the passage of the Mammography Quality Standards Act of 1992 (MQSA), which “provided the FDA with the legislative mandate to oversee the quality of the modality, setting an important precedent as the FDA generally doesn’t have quality jurisdiction.” As the perspective noted, the MQSA is “widely believed to have improved the quality of mammography.”
The House of Representatives held a hearing several months ago on medical radiation dose, and is considering the possible creation of legislative oversight, according to Smith-Bindman, who testified at the trial. “If Congress passes this legislation, the FDA could create standards for specific doses for specific exams, for example,” she said. “The agency could require that institutions demonstrate their capacity to meet these targets, as well as regulate and monitor facilities over time, which could lead to dramatic lowering of the radiation dose associated with CT.”
“There is ample evidence about how to lower dose with CT, but some standards are needed to lead to much more widespread application of those technologies,” Smith-Bindman continued. In the NEJM perspective, there are two chest CT studies—one that uses about one-tenth less radiation dose (dose-length product, 938 mGy per centimeter versus 88 mGy per centimeter; effective dose, 15.9 mSv versus 1.5 mSv) than a similar study.
Smith-Bindman also spoke to the lack of knowledge about dose-emission on the part of radiologists and technologists, and therefore, standardizing them “would improve compliance for low-dose studies.” The perspective stated that “technologists and physicians must be educated regarding the importance of minimizing doses, and comprehensible dose information must be displayed where diagnostic studies are done.”
Equally important, but difficult to monitor are cumulative radiation dose over the course of a patient’s life, especially a high-risk patient, and the various dose-lengths required for various procedures and body types. “Our health system is not conducive to knowing what happens to a patient over time,” said Smith-Bindman, who added that the FDA is considering making this information easily exportable into the patient’s EMR.
She acknowledged that the radiation dose a patient absorbs will vary according to individual characteristics, such as body mass index. However, “using evidence-based averages are generally better than having no data standard.” Also, a patient’s threshold will depend on the patient’s clinical characteristics, and Smith-Bindman suggested that a patient’s imaging history should be one criteria that providers consider when evaluating whether or not to administer a CT scan.
To further evaluate CT scanning and dose, her group is submitting a research grant to review several of these aspects, one of which is a comparative effectiveness study to assess when imaging is likely to be helpful and where it is likely to not be helpful. “The advanced imaging technologies are extraordinary, but now we have to assess when to use them that provides the most benefit to the patient without unnecessary radiation exposure or over imaging,” she concluded.