Idling MRIs overnight costs U.S. facilities millions, study says

Radiology is a major contributor to health care’s overall climate footprint due to its energy-intensive devices. Despite this, radiology departments tend to let magnetic resonance imaging (MRI) units idle rather than turning them off because of the time it takes them to start up and shut down, says Sean Woolen, M.D., a faculty member with the University of California San Francisco (UCSF). In some cases, equipment may remain in idle mode overnight and on weekends to allow time for software updates or over concerns around cooling. During that time, the equipment continues to draw massive amounts of energy.

To understand an MRI unit’s power demand when scanning, off, idle and in power-saving modes, Woolen partnered with Siemens Healthineers and Siemens Smart Infrastructure to monitor energy usage in UCSF’s department of radiology and biomedical engineering. In the resulting study, “Ecodesign and Operational Strategies to Reduce the Carbon Footprint of MRI for Energy Cost Savings,” published in the April issue of Radiology, they concluded that even the off mode may not be the most efficient solution.

The researchers equipped four outpatient MRI scanners from three different vendors with power meters. Monitoring revealed that switching MRI units from idle to off mode for 12 hours overnight could reduce power consumption by as much as 33%. This translates to a potential annual savings of up to 21 megawatt-hours, 14.9 metric tons of carbon dioxide equivalent and $2,943.

However, the researchers also drew upon previous research, conducted by Siemens with Switzerland’s University Hospital of Basel’s department of radiology and published in Radiology in 2020. The study, “The Energy Consumption of Radiology: Energy- and Cost-saving Opportunities for CT and MRI Operation,” indicated that one-third of MRI energy consumption happens in off mode, due to the need for constant cryogen circulation to cool superconducting magnets. The UCSF team determined that switching to power-save mode — which reduces power consumption by cycling the operations of the cold head compressor — rather than simply off mode during non-use hours could reduce consumption by an additional 22% to 28% more than off mode.

Using the power-save mode overnight has the potential to save an additional 8.8 to 11.4 megawatt-hours, or between $1,226 and $1,594 annually. The researchers determined that using the power-save mode overnight in all outpatient MRI units across the United States could save the U.S. health care field up to 76,288 megawatt-hours and as much as $10.7 million annually.

The first step to realizing these savings, the researchers note, is making it standard operating procedure to switch to the lowest power mode when equipment is not in use and configuring MRI units to go into off mode on a predetermined schedule.

Woolen notes that powering down the MRI units did not result in any additional maintenance or unexpected consequences. 

“One of the things we learned is that it is essential to incorporate the thoughts of MRI technologists, facilities engineers and industry partners into an implementation strategy,” he says. “Only by working together can the most effective strategy be made.”