CT switch for savings

Research shows that medical imaging has a substantial carbon footprint. Larger imaging modalities such as magnetic resonance imaging (MRI), angiography suites and computed tomography (CT) scanners use significant amounts of electricity that contribute to the carbon footprint of imaging.

A high proportion (up to 66%) of the energy use of CT scanners is whilst they are in an idle state. That is, the machine is waiting for a scan to be initiated, but not actually being clinically used. ¹ The total energy used by a CT scanner in idle state can be 14-30 times higher than the energy used for active scans. ² Although there is a need for a scanner to be available for emergency scanning at all hours, some scanners left switched on, may be unnecessary to clinical requirements. As Australia has the second highest number of CT scanners per capita in the world ³ and 115 of these scanners are found in New South Wales public hospitals, switching off scanners at appropriate times, presents an opportunity for potential savings. This would have no adverse impacts on patient health and reduce both carbon emissions and financial costs.

Turning off CT scanners when not in use

The CT switch off pilot project aimed to investigate potential carbon, financial and health service benefits of turning off a computed tomography (CT) scanner when not in use. The project was conducted at John Hunter Hospital in Hunter New England Local Health District (HNELHD). The project is the first intervention of its kind within HNELHD. The project team aimed to assess the impact of switching off a CT scanner outside normal scanning hours on:

• staff knowledge and attitudes
• health service delivery
• power consumption
• financial cost
• carbon footprint.

Prior to implementation, an audit was conducted to collate data on all HNELHD hospitals and assess opportunities to switch off CT scanners that were not in clinical use after hours. This involved assessing workload across an entire day and investigating any times where scanners were idle. Staff were surveyed to identify opportunities to generate energy savings based on their workflow and assessment of clinical load. From this data, a suitable CT scanner was identified that could be powered down during low use times.

An education and intervention package, informed by published research, was developed to demonstrate the impact of idle scanners regarding energy waste. Written reminders, emails and educational posters were distributed to staff and placed in clinical areas to encourage staff to make the change and embed the change behaviour in their teams. During the 7-day control period, there was no change to daily workload or restart/shutdown procedures. The scanner was left on overnight, and a reboot procedure was undertaken daily. During the 7-day intervention period, radiographers were asked to switch off the scanner at the end of the clinical worklist each day and switch the scanner on again the next morning. CT scanner data was collected over this period, and clinical workload was not altered at any time in the pilot period.

One small changes leads to significant savings

The project was successful in achieving energy, carbon and financial savings. These outcomes are aligned with international research which demonstrated similar outcomes. Over the course of one week, energy consumption was reduced by approximately 32%. This equates to 7,280 kWh saved annually. This energy saving was achieved by switching off the CT scanner when not in clinical use after hours. The hours switched off varied due to clinical load and staff availability.

The pilot project saves approximately 5.5tonnes CO₂e, which is comparable to the annual carbon footprint of two light vehicles. The cost savings are dependent on the scanner model, hours of operation and hospital’s energy provider. On the scanner used in the study, the estimated annual electricity cost savings were approximately $1,381. Whilst energy consumption varies greatly between different makes and models of CT scanner, the project is readily scalable and the energy, carbon and financial savings could be achieved at other sites. Two further sites within HNELHD are currently implementing this intervention. 80% of staff involved found no negative impact to their workflow. Some were also able to identify further areas to switch off equipment and ancillary devices leading to greater non-measured savings.

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