Contributed by
IPR '
Rick R. van Rijn - ESPR, and Michael Callahan - SPR .
History
The average US household emits 4.1 metric tons of carbon dioxide equivalents annually.
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Question
How many metric tons of carbon dioxide equivalents (CO2e) is produced on average by a single MRI system annually?
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Correct answer
Approximately 50 MT CO2e
Discussion
A recent Scoping Review by Woolen et al. evaluated radiology’s environmental impact. For this the authors included 115 studies, published from 1971 to 2025. The authors reported both energy consumption in megawatt-hour as well as carbon dioxide equivalent emission.
For reference they used a U.S. single family home that consumes 10.5 megawatt-hour (MWh) of energy and produces 4.1 metric tons (MT) of carbon dioxide equivalents (CO2e) annually. By far the most polluting modality is MRI which on average consumes 130.9 ± 31.7 MWh and produces 51.5 ± 12.5 MT CO2e annually. Here it is important to note that MRI systems were reported to be idle 76 – 91% of the time, using 33% of their energy in idle or off modes. The second ranking modality is CT which consumes 30.1 ± 7.0 MWh and produces 11.8 ± 2.8 MT CO2e annually. Here 88% of energy consumption occurred when the scanner was unoccupied, including 66% during idle or off modes. Other modalities used significantly less energy and produced significantly less CO2e.
The authors also report on the cost of cooling, where 4 MRI scanners and 3 CT scanners combined consumed 492,624 kilowatt-hour (kWh) annually. Which is responsible of 44.5% of total imaging energy consumption.
There are ways to reduce radiology’s carbon footprint. First and foremost by shutting down or powering down of systems outside office hours. With overnight MRI shutdown cutting energy consumption by 25% to 33% and CT shutdown saving approximately 47%. Note: while the MRI magnetic field always remains on, vendors offer a "stand-by" mode, which shuts down the cold head compressors when not scanning to save energy.
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References
- Woolen SA, Martin M, Foster CA, MacEachern MP, Maturen KE. Green Imaging: Scoping Review of Radiology's Environmental Impact. J Am Coll Radiol. 2026 Jan;23(1):123-135. doi: 10.1016/j.jacr.2025.09.013.