Aim. The aim of this study was to evaluate the clinical feasibility of three-dimensional gated blood pool scintigraphy (3D GBPS) on a 3D-ring cadmium zinc telluride (CZT) single photon emission computed tomography(SPECT)/computed tomography (CT) system for the assessment of left ventricular function. Clinical feasibility was evaluated in a patient study comparing 3D GBPS on a 3D-ring CZT SPECT/CT system to two-dimensional (2D) planar multigated acquisition (MUGA) on a conventional dual-head sodium iodide (NaI) gamma camera. Acquisition and reconstruction protocols were optimized for 3D GBPSon a3D-ring CZT SPECT/CT system for clinical application.

Methods. Patients referred for 2D planar MUGA to assess left ventricular function as part of their clinical work-up were prospectively enrolled. Patients received 550 MBq technetium-99m-labeled human serum albumin and underwent both 2D planar MUGA on a conventional dual-head NaI gamma camera and 3D GBPS on a 3D-ring CZT SPECT/CT system in direct succession. Left ventricular ejection fraction (LVEF), end-diastolic volume (LVEDV), and end-systolic volume (LVESV) were assessed on both systems. Correlations and systematic differences in LVEF, LVEDV, LVESV between the systems were evaluated. Acquisition optimization was performed by retrospectively reducing acquisition time using list-mode data, and assessing its impact on LVEF accuracy. Reconstruction parameters were optimized based on image quality and agreement of LVEF accuracy.

Results. Ten patients were included. An acquisition and optimized reconstruction protocol was established: 15-minute acquisition time, 16 RR bins, focus mode and ordered subset expectation maximization (OSEM) with 6 iterations, 10 subsets, voxel size 4.92 mm, no scatter correction, and no post-reconstruction filtering. 3D GBPS yielded significantly higher median LVEF values compared to 2D planar MUGA (73.5% vs. 61.5%, p < 0.05) and significantly lower LVESV values (22.0 mL vs. 46.0 mL, p < 0.05), while LVEDV values were comparable between modalities (91.5 mL vs. 93.5 mL, p > 0.05). Correlation between the two systems was poor for LVEF (ρ = 0.20), moderate for LVEDV (ρ = 0.46), and absent for LVESV (ρ = 0.10). No significant difference in LVEF was observed between 75% and 100% acquisition times, with the strongest correlation at 75% (ρ = 0.96). Significant differences and lower correlations were found at 50% (ρ = 0.92) and 25% (ρ = 0.82) compared to 100%.

Conclusion. 3D GBPS on a 3D-ring CZT SPECT/CT system yielded systematically higher LVEF and lower LVESV values compared to 2D planar MUGA on a conventional dual-head NaI gamma camera, indicating that the two methods are not interchangeable. Acquisition time could potentially be reduced by 25%, from 15 to 11 minutes, without affecting LVEF accuracy. Our findings suggest that 3D GBPS is clinically feasible, but further validation is required.

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.