Between 2011 and 2024, 13.5 million liters of contrast media were administered to Medicare beneficiaries for 169 million advanced imaging exams such as CT and MRI, according to a research letter published December 5 in JAMA Network Open.
The findings are sobering, as contrast use contributes to environmental pollution, according to lead author Florence Doo, MD, of the University of Maryland in Baltimore. Doo collaborated with colleagues from the Harvey L. Neiman Health Policy Institute (HPI), NYU Langone, and Oxford University and Imperial College London (both in the U.K.).
"Contrast agents are necessary for effective imaging, but they don't disappear after use," she said in a statement released by HPI. "Iodine and gadolinium are non-renewable resources that can enter wastewater and accumulate in rivers, oceans, and even drinking water. Quantifying which imaging exams use the most contrast helps us [develop] thoughtful, practical contrast stewardship strategies to ensure patients continue to receive safe and high-quality imaging care."
Contrast agents are critical for diagnosing disease from imaging exams, but they are also "persistent pollutants," Doo's group noted. As typical wastewater treatment does not fully remove them, concerns remain regarding their long-term ecological and public health impact.
The team conducted a study that included U.S. Medicare Part B fee-for-service public claims data from 2011 to 2024, using current procedural terminology codes (CPT) to identify imaging procedure types that used contrast (CT, CT angiography, MRI, MR angiography). It estimated contrast volumes using standard doses: 100 mL for iodinated agents and 15 mL for gadolinium-based agents.
Doo and colleagues found that during the study timeframe Medicare beneficiaries underwent 169 million contrast-enhanced imaging exams across 82 CPT codes (41 iodinated exams [50%]; 28 CT exams [68%]; 13 CTA exams [32%]; 41 gadolinium exams [50%]; 29 MRI [71%] exams; and 12 MRA [29%]) exams). These scans required 13.5 billion mL of contrast media.
They also reported that overall annual contrast volume increased, with mean year-over-year growth from 2014 to 2019 of 5.2% for iodinated agents and 3.5% for gadolinium agents. (The COVID pandemic resulted in declines in 2020, but these were followed by rebounds in 2021, with growth of 10.8% and 10.1%, respectively.)
The group noted that iodinated agents dominated total combined contrast volume, at 12.9 billion mL (95.6%), and that CT abdomen or pelvis represented the largest single contrast use contributor at 4.4 billion mL. For gadolinium agents, brain MRI took top place at 221 million mL.
Doo's group emphasized that there are "actionable mitigation strategies" for reducing environmental pollution from medical imaging, including confirming clinical appropriateness of imaging orders, using weight-based dosing to avoid excess use of contrast, and employing multiuse vial systems. The investigators wrote that biodegradable contrast alternatives and AI reduction algorithms have begun to emerge as ways to cut medical imaging pollution, although they stressed that "these methods are still experimental and require rigorous clinical evaluation and regulatory review."
In any case, the team's findings present a stark picture of the effect medical imaging has on the planet.
"We can't ignore the environmental consequences of medical imaging," Doo said. "Stewardship of contrast agents is a measurable and impactful way to align patient care with planetary health and should be an important part of broader health care sustainability efforts."
The full report can be found here.
Disclosure: Doo was supported by a grant from the National Institutes of Health Clinical and Translational Science Award Program and the Association of Academic Radiology Clinical Effectiveness in Radiology Research Academic Fund, which is partly funded by GE Healthcare.
