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Measuring the carbon footprint of molecular imaging  

Project starts to provide a benchmark, identify hotspots, and target reduction efforts and it is part funded by Institute of Physics and Engineering in Medicine (IPEM).
Mobile PET-CT scanner Stevenage

Mr Mark Cracknell, Radiographer Paul Strickland Scanner Centre; Gerry Lowe, Medical Physicist the Mount Vernon Cancer Centre and Robert Chuter, Principal Clinical Scientist from The Christie Hospital, Manchester, are embarking on a sustainability project to measure the carbon footprint of SPECT and PET-CT scans for a single patient. The aim of the project is to provide a benchmark, identify hotspots, and target reduction efforts and it is part funded by Institute of Physics and Engineering in Medicine (IPEM) www.ipem.ac.uk

The NHS contributes to 5% of UK carbon emissions, according to NHS England. The health service has set ambitious targets to reach net zero by 2040, with an 80% reduction by 2028 to 2032 for emissions directly controlled by the NHS. For emissions that the NHS can influence, the aim is to reach net zero by 2045, with an 80% reduction by 2036 to 2039. 

The team will use a “bottom-up” approach, which involves identifying and quantifying all materials and processes involved for a single patient (activity data). Once the activity data has been collected, Emission factors will be used to convert the activity data into carbon dioxide equivalent (CO2e). Data are being acquired from Paul Strickland Scanner Centre activity, and the team are also inviting other centres throughout the UK to contribute their data in order to make the final dataset more generalisable. 

The power consumption of different devices around the Paul Strickland Scanner Centre PET-CT department was calculated using a readily available power monitor.  

The consumables used for a typical cannulation were weighed, and then a conversion factor applied. Consumables associated with the automatic injector (used to inject the PET radiopharmaceuticals) were also weighed, to be converted into CO2e. 

Data from Energy Meters connected to each scanner were collected and compared with the number of patients scanned to calculate energy use in kWh per patient.  

Over a two-week period, the amount of waste produced in PET-CT was weighed and recorded according to each type (General waste, Clinical Waste, Recycling). The number of patients for the previous day was also noted, to calculate waste per patient. Conversion factors according to the method of disposal will then be applied to calculate the CO2e for waste produced per patient. 

Patient travel data will be collected via a questionnaire, with the intention to survey 200 patients over a two to three month period. Patients will be asked from where they are travelling for their appointment and what mode of transport they used. A similar survey will be sent to PET-CT staff. The CO2e will then be calculated using the Green House Gases emissions factor for the mode of transport, available from the BEIS/DEFRA database. 

Future work includes collecting energy consumption data for A/C units and including the carbon footprint for the production and delivery of radioactive tracer. The team hopes to produce the results by the end of 2024. This project represents a significant step towards understanding and reducing the environmental impact of medical imaging. 

If you would be able to provide data for your PET-CT or SPECT department, or would like to comment on this work, please get in touch by emailing mark.cracknell@nhs.net or gerry.lowe@nhs.net 

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