Angiography imaging systems that are the center-piece of the interventional cardiology or electrophysiology labs consume a fair amount of energy during procedures and still draw power when sitting idle. There have been growing discussions across healthcare about and among vendors of how to go green by making operations for environmentally friendly by reducing carbon emissions through reduced electrical consumption. But there also are sizable electric bill cost savings that cardiology departments could achieve by just turning these systems off at night.
Unlike buying a new washer or hot water heater, there are no Energy Star ratings to show cost savings when shopping around for angiography systems or to compare with older installed systems. This prompted researchers at the University Hospital Basel in Switzerland to assess what their actual power consumption is and estimate what this means in terms of energy costs and carbon emissions. They also took it a step further to assess cost savings if these systems were powered down completely when they are not being used rather than running 24/7. The study was published this week in then American Journal for Roentgenology (AJR).[1] The team added power sensors to the university's seven Siemens fluoroscopy systems used by the interventional cardiology and EP catheterization labs, interventional radiology, neurointerventional, radiology, and two urology fluoroscopy units.
"A hypothetical operational adjustment whereby all systems would be switched from the idle to off state overnight and on weekends (vs operated in idle mode 24/7) would yield potential annual savings in energy consumption of 144,640 kWh, carbon emissions of 18.6 MtCO2eq, and electricity costs of $37,896," wrote the research team and lead author Jan Vosshenrich, MD, a consultant radiology at the University Hospital Basel, and a postdoctoral research scholar at NYU Langone Health.
Details of the fluoroscopy imaging system power consumption study
The researchers said energy consumption of interventional imaging systems is usually estimated using manufacturer-provided specifications rather than by direct measurement. The University of Basel has a longstanding practice of powering down its imaging systems, including interventional systems, at the close of each workday. They are powered up as needed for emergencies. This allowed comparisons of energy savings and off-hour power consumption if the systems were left powered up, but idle.
The radiology and cardiology department systems have had power sensors installed since 2018 as part of the hospital's efforts to monitor and curb power usage. For this study, data from these systems was collected for a four-week period in 2022. The systems in urology were temporarily equipped with power measurement sensors for two-weeks in the summer of 2023.
The data show these seven systems had a combined projected annual energy consumption of 115,684 kWh. The authors said this corresponds to the annual energy use of 23 four-person households.
The projected annual energy consumption for each system in radiology and cardiology depended on usage, but was between the same annual energy consumption of four to five, four-person households. The urology systems each equalled the same energy use as one, four-person household per year.
Surprisingly, if these systems were maintained as they are at many hospitals where they remain in idle or low-power modes 24/7, the off-hour power requirements would have made up 60.3% of of the projected total energy consumption, researchers said.
Additional power savings could be realized from MRI and CT
The investigators based this angiography system study on prior radiology studies for MRI and CT system power consumption. Vosshenrich et al. wrote that the mean power draw of a CT scanner in the off state is about 0.5 kW, and in the idle state about 3 kW. For comparison, the mean annual energy consumption of a four-person household is about 5,000 kWh, and mean annual energy consumption of a CT scanner of 26,226 kWh.
Researchers wrote the cost savings potential is even higher for MRI systems that consume much more power. The mean power draw of an MRI scanner in the off state without power-save mode of 8.9 kW, and in the idle state 12.9 kW.
The healthcare industry is responsible for an estimated 7.6% of U.S. and 4.4% of global carbon emissions. Medical imaging systems are one of the biggest drivers in this footprint because of their high amount of consumption.
"The amount of electricity and corresponding greenhouse gas emissions are massive. So putting that in the context, one MRI scanner is equivalent to several hundred gasoline powered vehicles being driven average use over the course of a year. Most departments have more than one scanner and if you scale that up across the country, you can see the substantial impact," explained Kate Hanneman, MD, MPH, FRCPC, a cardiothoracic imager, vice chair of medical imaging research, and an associate professor at the University Of Toronto, and deputy lead of sustainability at the joint department of medical imaging, Toronto General Hospital. She has been involved in several studies examining the carbon footprint of radiology and how to make medical imaging more sustainable. She also chaired a session on this topic at RSNA 2023 and spoke to Cardiology Business in an interview.
"The energy consumption varies very much by modality. So MRI is much higher than CT, and CT is much higher than ultrasound, and ultrasound is even higher than X-ray. So when you think about the imaging that we're doing, you really have to be mindful of that. I think we have a responsibility to start thinking about what we can do to minimize that," Hanneman said.
She noted there is increasing interest in how radiology and cardiac imaging systems, which are major power consumes at hospitals, can play a role in reducing costs and and to reduce a health system's overall carbon footprint.
"Our equipment uses a lot of energy when we are acquiring images, but also overnight if we're not turning off or powering down our machines. That energy mix has a really large amount of greenhouse gas emissions associated with it. So we are a major contributor to greenhouse gas emissions when you look at healthcare more broadly," Hanneman explained.
Several vendors at RSNA were also touting how their latest imaging systems can help save energy costs and make health systems more environmentally friendly.
Dave Fornell has covered healthcare for more than 17 years, with a focus in cardiology and radiology. Fornell is a 5-time winner of a Jesse H. Neal Award, the most prestigious editorial honors in the field of specialized journalism. The wins included best technical content, best use of social media and best COVID-19 coverage. Fornell was also a three-time Neal finalist for best range of work by a single author. He produces more than 100 editorial videos each year, most of them interviews with key opinion leaders in medicine. He also writes technical articles, covers key trends, conducts video hospital site visits, and is very involved with social media. E-mail: dfornell@innovatehealthcare.com