A NEJM study generating a lot of buzz by Fazel et al reported substantial doses of ionizing radiation exposure in patients undergoing medical imaging exams. While researchers found high cumulative effective doses more frequently in older adults, rates for high and very high doses were not trivial in younger adults – with more than 30 percent of men and 40 percent of women who received doses exceeding 20 mSv per year being under the age of 50 years.
SPECT myocardial perfusion imaging (MPI) topped the list of the 20 procedures with the largest contribution to the annual cumulative effective dose from medical imaging procedures (22 percent). The average dose per person for MPI was estimated at 15.6 mSv.
CT angiography of the chest (noncoronary), with an average dose of 15 mSv, accounted for 3.1 percent of the total effective dose. Diagnostic cardiac cath, with an average dose of 7 mSv, accounted for 4.6 percent of the total effective dose. Interventional coronary cath procedures, with an average dose of 15 mSv, accounted for 3.1 percent of the total effective dose.
To put these numbers in perspective, CT (all studies including head, neck, abdomen, etc.) and nuclear imaging accounted for 21 percent of the total number of procedures, and 75 percent of the total effective dose. In contrast, procedures related to radiography made up 71 percent of the total number of procedures performed, but only 10 percent of the total effective dose. When examined according to anatomical site, procedures of the chest accounted for 45 percent of the total effective dose.
These numbers are based on claims data during the years 2005 to 2007 from five healthcare markets. Unfortunately, researchers do not separate out coronary CT angiography (CCTA). Recent studies have documented effective doses as low as 2 mSv. But, Fazel et al results pointed more to cumulative radiation exposure from a lifetime of medical imaging. Of particular concern are younger patients who have the lifespan ahead of them to develop cancer based on the established theoretical risk.
No medical imaging modality is an island unto itself. It is incumbent upon the industry and healthcare providers to find ways to track radiation exposure and “red flag” those who exceed a determined radiation exposure threshold or number of exams (CT, nuclear, diagnostic cath). Some insurance companies have initiated such programs with success.
The NIH recently undertook a mission to work with its IT vendors to transfer radiation exposure data directly to patients’ EMR. The FDA recommends that patients carry an “exposure card” that documents exam type, date, reason and radiation exposure. The patients can then present this card during each imaging exam.
Over the last several years, healthcare providers and industry have developed many methods to decrease the amount of radiation exposure to patients undergoing medical imaging tests. Now it’s time to be smart with this information. Such data must be integrated into hospital-wide IT systems and used as quality metrics. Fazel’s study is a good reminder of where we are and where we need to go.
There are a number of studies we are highlighting in this portal that document the benefit of CCTA when used judiciously in the right patient population. And check out the article on buying refurbished PET scanners as a way to stay competitive without spending more money than what you have.
On these or any other topics, please send me your comments. I look forward to hearing from you.
Chris P. Kaiser, Editor