Planetary Health and Climate Action in Radiology

Reduce the Need for Resource Intensive Hospital Care

The provision of care in the hospital setting requires a significant use of resources and energy, with a study from the United Kingdom demonstrating that the average inpatient admission produces 125 kg of CO₂ equivalents per day. ²⁸ Both from a patient outcome and sustainability perspective, it is imperative that healthcare practices are shifted away from reactive care to a focus on preventive care. For patients and providers, this includes health promotion at both a micro (personal) and meso (facility or regional) level such as advocating for active transportation and plant-based foods for the home, work, and when being cared for at the hospital. The provision of effective screening programs can also promote preventative/early less-intensive care. In the case of breast cancer, recent recommendations by the US Preventative Services Task Force state that women from the ages of 40 to 74 years receiving biennial screening mammography will result in an average of 165 life-years gained among a cohort of 1000 women (just over 8 deaths averted). ²⁹ In the case of lung cancer, screening guidelines recommend annual low-dose CT among heavy smokers from the ages of 55 to 74 years as evidenced by a 20% reduction in lung cancer-related death. ³⁰ While the environmental impact of screening radiographs and CT scans are not negligible (mean carbon emissions of 0.76 and 9.2 kg CO₂ equivalents per scan, respectively), screening programs can help mitigate the costly care downstream from advanced cancer and complex inpatient hospital management. ³¹ There is an argument to be made that screening programs through reducing mortality may paradoxically increase an individual’s lifetime carbon footprint and only delay inevitable end-of-life care (and its associated high carbon footprint), but from an ethical and environmental standpoint, improving patient outcomes while mitigating upfront environmental impacts are central to the importance of effective secondary prevention, while also providing more time for mitigation and adaptive strategies to develop and take effect. ³²

Match Supply of Imaging Services to Demand

The increasing volumes and growing demands on radiology departments across the nation cannot be understated; from 2017 to 2040, the number of CT examinations is expected to more than double from 5.6 million to 11.9 million and the number of MRI examinations is forecasted to experience even further growth from 1.9 million to 5.3 million. ³³ Imaging deemed to be “low value”—in other words, performed without an appropriate clinical indication, achieving little to no value in patient management decision making, and ultimately resulting in healthcare resource waste—is pervasive and estimated to account for 2% to 24% of imaging studies in Canada. ³⁴

Strategies for the reduction of low value imaging have been proposed and thus would drastically mitigate the planetary health impact of medical imaging. Firstly, the implementation of point-of-care clinical decision-making tools and guidelines such as the American College of Radiology (ACR) Appropriateness Criteria are evidence-based means of ensuring appropriate testing and reducing waste at the point of requisition by the ordering provider. The CAR endorses its own top 5 recommendations for reducing low-value imaging and has created referral guidelines for appropriate imaging across several sections such as musculoskeletal, trauma, and breast imaging. ³⁵ Central intake offices are models which pool and streamline advanced imaging referrals across regional facilities, reducing duplicate exams, prolonged waitlists, and transportation to distant sites. Central intake offices present a unique opportunity which can be coupled with clinical decision-making tools and appropriateness guidelines to standardize the provision of medically necessary care. For example, a central intake office is an effective means in which to apply appropriateness guidelines, such as not performing MRI exams for hip and knee pain in adults if severe osteoarthritis is seen on a radiograph, which in one study reduced unnecessary hip and knee MRIs by 21%. ³⁶ A recent review of value-based radiology in Canada outlines strategies to reduce low-value imaging and provides a summary of recommended actions. ³⁵

Appropriate follow-up for incidentally detected findings can help limit the provision of subsequent low value imaging. The ongoing development and implementation of guidelines such as the ACR White Paper on Managing Incidental Thyroid Nodules or the CAR Recommendations for the Management of Incidental Hepatobiliary Findings in Adults are critical to reducing unnecessary extra examinations and each of its downstream effects beyond improving the individual patient’s care.^37,38 In concert with reducing waitlists through guidelines, clinical decisions making tools, and central intake offices, advocacy for the provision of adequate imaging capacity and effective imaging efficiency (ie, schedule optimization to reduce scanner idle time between patients) may reduce the burden of delayed medically necessary tests, and thus mitigate more intensive care for sicker patients (compounding the effects as described in framework item 1).

Reduce Environmental Impact of Medically Necessary Care

When imaging examinations are appropriately indicated, it is imperative that each study’s relative environmental impact be considered in part of the clinical decision-making process. In medical education and primary care, there is a growing emphasis on the financial aspects of low-value care such as routine bloodwork. For example, there is increasing acknowledgement of the financial cost of vitamin D testing, which is estimated to be unnecessary in up to 75% of cases and amount to $30 million annually in Canada. ³⁹ As patients and providers become more cognisant of the financial ramifications of medical care, a similar paradigm shift in perspective must be made regarding literacy around healthcare’s climate impact. Leadership by professional medical organizations and policymakers is essential. A recent CAR Statement on Environmental Sustainability in Medical Imaging provides specific recommendations to guide radiologists, medical imaging operations and administrative teams, industry partners, and government in transforming to low carbon, high quality, climate resilient medical imaging in Canada. ⁴⁰

Mitigation strategies are centred on reducing overall energy consumption and reducing unnecessary waste. As such, the simple yet substantial impact of powering down medical imaging machines when not in use is an ideal mitigation target. ¹⁹ The cumulative energy use of medical imaging equipment is considerable, with a single radiology department in Switzerland reporting that the energy consumption of its 3 computed tomography (CT) and 4 magnetic resonance imaging (MRI) machines was equivalent to 4% of the hospital’s total energy use. ⁴¹ In other terms, one CT scanner was equivalent to the annual power used by 5 four-person households and one MRI scanner was equivalent to 26 four-person households. ⁴¹ Moreover, energy consumption of these machines in standby state accounted for two-thirds of the total CT energy use and one-third of the total MRI energy use. ⁴¹ When possible, optimizing low energy idle and system off states, particularly for CT, is of utmost importance and should be an area of focus among radiologists, technologists, and industry partners. A predominantly outpatient practice environment is the optimal scenario for this mitigation strategy, as demonstrated by a recent Canadian study which found that powering down a single CT scanner during non-operational times overnight and on Sundays resulted in annual savings of 14 180 kWh. ⁴²

Beyond the medical imaging scanners themselves, taking advantage of radiology department workstation devices and interventional rooms when non-operational is critical. In a United States study of all workstations in a single radiology department, it was reported that turning off the radiology computers and monitors at the end of a workday and on weekends amounted to a 76% reduction in energy consumption. ⁴³ In another study evaluating the energy use of 32 workstations in a single department, a simple adjustment in device configuration to shut down after 1 hour of inactivity (as opposed to the default of entering a stand-by mode after 4 hours of inactivity) correlated with a 45% reduction in energy use. ⁴⁴ When interventional radiology suites are not in use, allowing greater fluctuations in temperature and limiting climate control and air change systems can significantly reduce energy consumption.^19,45

Addressing Scope 3 (supply chain) emissions in radiology will require transition to a circular economy model. Current linear supply chain procurement involves resource extraction, manufacture, transportation, single use and disposal, creating continuous demand for raw materials and landfill/incineration. In a circular supply chain, products are reused, repurposed, and recycled to next best use, minimizing resource consumption and waste generation. The 5 R’s of waste hierarchy (refuse, reduce, reuse, repurpose, recycle and lastly dispose) place emphasis on waste prevention over disposal.^46,47 At the production and packaging steps, switching from single-use to multi-patient CT contrast delivery systems has been shown to reduce contrast waste by 73%, plastic waste by 93%, and cost by 35%. ⁴⁸ Establishing a circular supply chain is a multi-step and industry collaborative process but can be achieved through examples such as creating contrast medium recycling pathways, switching from disposable to reuseable medical supplies, and optimizing the efficiency of imaging scanners in recapturing finite resources.^19,49

When imaging is appropriately indicated, choosing lower-energy imaging tests may provide a similar degree of diagnostic clarity, while potentially reducing carbon emissions by over 17-fold such as in cases of suspected uncomplicated acute cholecystitis or appendicitis in which ultrasound (emitting an average of 0.53 kg CO₂ equivalents) may avert the use of a CT scan (emitting an average of 9.2 kg CO₂ equivalents). ⁵⁰ Additionally, abbreviating imaging protocols can lead to substantial reductions in emissions with potential benefits of improved patient experience and reduced waitlist times. For example, using an abbreviated cardiac MRI protocol with a change in the timing of certain sequences after contrast administration leads to savings of 8 minutes per scan and the downstream energy savings equivalent to 27 homes annually if implemented across the United States. ⁵¹

Innovative means of providing portable and low-energy imaging can help reduce the climate impact of excessive transportation. In Canada, transportation is responsible for 22% of national GHG emissions, presenting a major sustainable opportunity by optimizing both patient and provider transportation needs. ⁵² In rural and remote communities of Northern Saskatchewan, the implementation of a remote telerobotic ultrasound program yielded a diagnostic study in 70% of cases, minimizing unnecessary travel, improving wait times, and reducing disparities in imaging accessibility. ⁵³ Furthermore, following the implementation of a low-energy, portable MRI machine (0.064 tesla) in a remote Ontario community, it was found that patient transfer to another centre for fixed MRI examination could be deferred in over half of their cases, correlating to significant mitigation in GHG emissions and approximately $854 841 in savings per 50 patients annually. ⁵⁴

Lastly, adaptation to the now unavoidable impacts of the climate crisis is essential for all medical imaging departments. Complete description of adaptation measures is beyond the scope of this paper, however, should include backup systems to prevent power and data loss, up to date disaster response protocols, building structural preparedness against floods, extreme heat, and wildfire smoke as well as workforce planning for increased demand and to anticipate healthcare worker shortages. Collaborative action on adaptation measures requires education and engagement of front line radiology team members including radiologists and technologists, facility operations and medical administration, as well as regional, national, and global radiology organizations. A recent statement by the CAR highlights the need to integrate climate change knowledge into the Canadian Radiology educational curricula. ⁵⁵ Further adaptive efforts should lean heavily into structural preparedness of buildings against natural disasters, developing protocols and back-up systems in the event of disasters or power loss, and applying an iterative approach which assesses and continually improves upon ongoing sustainable initiatives.