Excess imaging translates to "significant" carbon dioxide (CO2) emissions, according to a study published March 28 in the Journal of the American College of Radiology.
How significant? Up to 129 kilotons of emissions annually -- the same as would be produced from powering a town of more than 70,000 people for a year, according to a statement released by the Harvey L. Neiman Health Policy Institute (HPI), which sponsored the research.
This statistic underscores how crucial it is to take action, said study co-author Julia Schoen, MD, of University of Michigan Health in Ann Arbor.
"Emissions are likely to continue to increase given sustained increases in overall imaging volumes over the past decade, and the potential for further increases related to climate-change-related exposures and events," she noted.
Previous studies on inappropriate imaging have focused on "the importance of minimizing patient radiation exposure, limiting patient discomfort, lost work time, use of resources efficiently, and reduction of overall healthcare expenditures," the group explained.
"Overuse of imaging is a strain on our healthcare system and radiology workforce," said senior author Michael Atalay, MD, PhD, of Brown University in Providence, RI. "Estimates of excess imaging range from 4% to 30% of all imaging exams, which carries a heavy economic toll."
But this work is the first to estimate the carbon emissions of inappropriate imaging, and it highlights an additional reason to reduce unnecessary imaging, according to the investigators. Led by Gregory Cavanagh, MD, of Lahey Hospital and Medical Center in Burlington, MA, the group explored just how much excess greenhouse gases medical imaging produced between 2017 and 2021, using information from HPI's Neiman Almanac (an online data tool that collects data on annual imaging utilization for 100% of the nearly 30 million Medicare Fee-For-Service [MPFS] beneficiaries) to track the yearly total number of imaging studies. The team then calculated rates of excess imaging using data from the Rand Corporation on inappropriate use of CT and MR imaging, the highest emission modalities.
The researchers reported that the imaging inefficiency rate varied by modality and body region and ranged from 1.1% to 78.9%. They also found that total average yearly greenhouse gas emissions from all Medicare imaging exams between 2017 and 2021 ranged from 8.1 to 136 kilotons for MRI; 25 to 178 kilotons for CT; 7.1 to 46 kilotons for x-ray, and 2.7 to 23 kilotons for ultrasound. (Again, 129 kilotons of emissions would be produced from powering a town of more than 70,000 people for a year.)
Total yearly estimated greenhouse gas emissions from inappropriate imaging exams performed during the time frame measured by the study -- across all modalities -- was 3.55 to 129.2 kilotons per year. Unnecessary CT exams made up roughly half of these excess emissions, while another quarter resulted from MR imaging.
"We calculated the range of possible emissions in our work," Cavanagh said. "The low-end estimates only included energy used during an exam, whereas the high-end estimates also included the energy required when the scanners are in standby mode or in production phase between scans."
The results add further evidence that decreasing unnecessary imaging can have a strong positive effect, according to the authors.
"Our analysis demonstrates the potential to meaningfully reduce our carbon footprint by decreasing low-value imaging," they concluded. "This would also decrease the risk and cost to patients, cost to the healthcare system, and radiology workforce shortage contributions from low-value imaging."
The complete study can be found here.
