Feasibility of ultra-low activity 18F-FDG PET/CT imaging in children.

Objectives: To investigate the feasibility of pediatric 18F-FDG total-body PET/CT imaging with an ultra-low activity and explore an optimized acquisition time range.

Methods: A total of 38 pediatric patients were prospectively enrolled and underwent dynamic total-body PET/CT imaging using ultra-low 18F-FDG activity (0.37 MBq/kg). The 60-minute list-mode raw data were acquired and then reconstructed as static PET images by using 50-51, 50-52, 50-53, 50-54, 50-55, 50-58, 50-60, and 45-60 minutes data, which were noted as G1, G2, G3, G4, G5, G8, G10, and G15, respectively. Image qualities were subjectively evaluated using the Likert scale and were objectively evaluated by the quantitative metrics including standard uptake value (SUV), signal-to-noise ratio (SNR), target-to-background ratio (TBR), and contrast-to-noise ratio (CNR).

Results: The injected activity of FDG was 13.38 ± 5.68 MBq (4.40-28.16 MBq) and produced 0.58 ± 0.19 mSv (0.29-1.04 mSv) of effective dose. The inter-reader agreement of subjective image quality was excellent (kappa = 0.878; 95% CI, 0.845-0.910). The average scores of image quality for G1-G15 were 1.10 ± 0.20, 2.03 ± 0.26, 2.66 ± 0.35, 3.00 ± 0.27, 3.32 ± 0.34, 4.25 ± 0.30, 4.49 ± 0.36, and 4.70 ± 0.37, respectively. All image scores are above 3 and all lesions are detectable starting from G8. SNRs of backgrounds, TBRs, and CNRs were significant differences from the control group before G8 (all P < 0.05).

Conclusion: The image quality of the 8 min acquisition for pediatric 18F-FDG total-body PET/CT with an ultra-low activity could meet the diagnostic requirements.

Advances in knowledge: This study confirms the feasibility of ultra-low dose PET imaging in children, and its methods and findings may guide clinical practice. pediatric patients will benefit from reduced radiation doses.