No single change agent is responsible for a 15 to 20% reduction in medical radiation doses to U.S. patients, but this significant stride — over a 10-year period — can be largely credited to greater awareness and reporting efforts led by the radiology community.

In November 2019, the National Council on Radiation Protection and Measurements (NCRP) issued Report No. 184, “Medical Radiation Exposure of Patients in the United States.”* The report revealed that most medical imaging doses are stable or decreasing — in stark contrast to a previous NCRP report showing a six-fold increase in radiation doses from the early 1980s up to 2006.
That report spurred a spate of initiatives, including the Dose Index Registry (DIR), Image Wisely® and Image Gently® — and increased radiation dose awareness overall, according to Mythreyi Chatfield, PhD, ACR EVP for quality and safety and a member of the NCRP committee that authored the report.

Practices in nuclear medicine had the biggest impact on the dose reduction — where the radiation dose per person decreased by more than 50% — largely because of fewer procedures within cardiac nuclear medicine. On the other hand, the number of CT scans increased by 20% over the 10-year period, but the average dose to the patient per CT exam went down by 6%.
Facilities use the DIR to compare their CT dose indices to regional and national values. The facilities then receive quarterly feedback reports comparing their results to aggregate results by body part and type of exam.

“The new report shows the average radiation dose per person has decreased,” says Mahadevappa Mahesh, MS, PhD, FACR, chair of the ACR Commission on Medical Physics (who also served as vice chair of the NCRP committee that authored the report). “We need to build on this moving forward. We have to keep up awareness of the need to optimize imaging protocols to minimize radiation risks — at the same time maintaining high image quality.”

The report notes technological advances that provide higher-quality images at lower doses. “If you look at scanners from, say, 10 years ago, some of those delivered four times the dose,” says Fred A. Mettler Jr., MD, FACR, chair of the NCRP committee tasked with completing NCRP 184, and clinical professor of the department of radiology and nuclear medicine at the University of New Mexico School of Medicine.

“As that equipment is getting replaced, those doses are coming down,” Mettler says. “By the College having registries — more than 5 million entries in the CT registry, for instance — we can now see the state of practice regarding dose,” he says. “This registry data empowers radiologists to really have an impact on patient care.” “Efforts to increase dose awareness among the medical community and the public are having a strong effect in terms of dose optimization and reduction,” Mahesh says. These initiatives include raising awareness of appropriateness guidelines, increasing access to dose registry data, and implementing mandatory accreditation of imaging facilities.

There is still more to learn when looking forward. “While we have more data on dose indices for CT from the DIR, working on this report exposed huge knowledge gaps in how we track some of the other procedures with ionizing radiation,” says Chatfield.

To fill these gaps, the ACR is piloting an IR/fluoroscopy and computed and digital radiography component of the DIR. “This will provide better information on the dose indices for the next refresh of the NCRP report,” Chatfield says. Interventional doses are difficult to quantify, with different patients getting different doses for different scans.
“Data on the number of procedures in IR — collected in a way that is meaningfully applicable to the national exposure measures — is simply not available. We need to work on systematic and coordinated tracking of data if we want to improve reliability of our estimates,” Chatfield says.

“It is encouraging to see that, 10 years later, initiatives to manage radiation exposure have largely been successful,” Chatfield says. The new report notes, however, that factors such as payment models, new regulatory guidelines, and technological advances should be assessed further to ensure the accuracy of dose estimates in future reports.

While the news is good, it is important not to become complacent, Mahesh says. All radiologists are encouraged to access and read the report at bit.ly/NCRPReport_No184.

Moving forward in keeping doses low — or reducing them further — requires close interactions between radiologists, medical physicists, and RTs. Mahesh says, “Members should put to use the tools ACR offers to monitor and improve upon radiation dose — and its dedication to an overall reduction of radiation doses to patients in the future.”

* NCRP Report No. 184 is a 10-year update to an NCRP report published in 2009. The current report updates medical radiation exposure information with data collected between 2006 and 2016.