PET is an energy hog, but relatively rare utilization lessens its carbon footprint. MRI and CT have no such ‘out’
Medical imaging machinery uses a lot of power, and the extent to which it quickens the pace of global warming is becoming clearer.
Radiology researchers at the University of Toronto have clarified the picture by quantifying greenhouse gases emitted by seven imaging modalities over a five-year period across their department, which serves five hospital sites.
The modalities the team tracked were X-ray, mammography, diagnostic ultrasound, CT, MRI, SPECT and PET.
Their key finding: Greenhouse gas emissions at their institution equaled the volumes discharged by 422 single-family homes or 770 gasoline-powered passenger vehicles driven for one year.
MRI was the most conspicuous energy consumer over time, pumping out 41% of all greenhouse gases over the study period despite accounting for only 12% of all imaging exams. CT was not far behind, at 34% of the five-year total.
PET was far and away the “worst offender” on a use-by-use basis. However, its utilization represented just 1% of all exams over the study period (2018–22).
Similarly, SPECT proved a heavy emitter but only figured in 3% of all imaging procedures, mitigating its ratio of the five-year total.
Here’s a rundown of the seven modalities in order of average estimated metric tons of carbon dioxide equivalents (CO2e) per year.
- PET: 60.5 kg CO2e
- MRI: 18.6 kg CO2e
- SPECT: 13.0 kg CO2e
- CT: 7.9 kg CO2e
- US: 0.85 kg CO2e
- X-ray + mammography (combined): 0.65 kg CO2e
Corresponding author Kate Hanneman, MD, MPH, and colleagues note several limitations in their study design. Among these were the study’s single-system focus and its concentration on diagnostic exams to the exclusion of interventional procedures.
The authors call for further study incorporating direct energy measurements for each modality, “including a range of indications and comprehensive life-cycle analysis for both diagnostic and interventional radiology.”
They conclude:
‘Given that MRI and CT are associated with the highest proportion of greenhouse gas emissions, initial environmental sustainability efforts in radiology departments can be targeted to these modalities.’
The Canadian Association of Radiologists Journal published the study May 14 and is making it available in full for free.
Dave P. has worked in journalism, marketing and public relations for more than 30 years, frequently concentrating on hospitals, healthcare technology and Catholic communications. He has also specialized in fundraising communications, ghostwriting for CEOs of local, national and global charities, nonprofits and foundations.