Objective:
This pilot study aims to assess the environmental impact of Positron Emission Tomography/Computed Tomography (PET/CT) imaging, in the context of efforts to mitigate climate change. This is studied by investigating the energy usage, waste generation, and the radiopharmaceutical production.

Methods:
Power measurements of the PET/CT scanner were conducted over four weeks and during different power settings (system on, computers off, software shutdown and energy saving mode) with a power analyzer. Various outcome measures, such as energy and cost savings per hour, energy consumption per PET/CT radiopharmaceutical procedure, and total annual energy consumption in two distinct scenarios, were calculated. Additional power measurements of reporting stations and desktop computers were performed in off-mode, sleeping mode and active mode. The data for waste disposal was collected by counting and weighing consumables used for a Fluorine-18 Fluorodeoxyglucose ([18F]FDG) procedure. Waste streams were identified and the data categorized per waste stream. The workflow for producing the [18F]FDG radiopharmaceutical was mapped out and data on the energy consumption of the cyclotron and cleanrooms and waste generation was collected. All data was finally expressed in CO2-equivalents (CO2-eq) by using emission factors.

Results:
Of the four different PET/CT power settings, the energy saving mode showed the most significant energy reduction compared to system on, resulting in ∼30% energy savings and a 0.94 kg CO2-eq emission reduction per hour. Furthermore, the energy consumption of various radiopharmaceutical procedures showed results ranging from 3.03 (2.90-3.09) to 5.15 (5.00-5.41) kWh/procedure (1.90 to 1.12 kg CO2-eq). The reporting stations and desktop computers showed both a ∼71% energy reduction in shutdown mode compared to system on. Correct waste separation of plastics and paper showed a ∼64%
CO2-eq reduction per procedure. For radiopharmaceutical production, the impact of the cyclotron’s energy consumption was found the largest (0.44 kg CO2-eq/procedure) compared to HVAC energy consumption (0.13 kg CO2-eq/procedure) and waste disposal (0.003 kg CO2-eq/procedure).The total environmental impact of [18F]FDG PET/CT imaging was measured at 2.01 kg CO2-eq per procedure, with PET/CT scanner energy consumption (62%) and cyclotron energy consumption (22%) being the primary contributors.

Conclusion:
This study showed that the environmental impact of PET/CT imaging is substantial and that it can be reduced by implementing energy saving strategies during non-operational hours, improving waste segregation for recycling and optimizing the energy efficiency of cyclotrons and cleanrooms. Furthermore, hospitals and manufacturers can even reduce the impact further by addressing opportunities such as using eco-friendly or recycled materials and incorporating green energy sources for power supply. Future research should focus on increasing energy-efficiency of scanners, cyclotron and HVAC systems, reducing the scan length and reducing low-value scanning to further decrease the environmental impact of PET/CT imaging while maintaining high diagnostic standards.