Evaluation of pediatric malignancies using total-body PET/CT with half-dose [ 18 F]-FDG

Purpose To explore the impact of a true half dose of [ 18 F]-FDG on image quality in pediatric oncological patients undergoing total-body PET/CT and investigate short acquisition times with half-dose injected activity. Methods One hundred pediatric oncological patients who underwent total-body PET/CT using the uEXPLORER scanner after receiving a true half dose of [ 18 F]-FDG (1.85 MBq/kg) were retrospectively enrolled. The PET images were first reconstructed using complete 600-s data and then split into 300-s, 180-s, 60-s, 40-s, and 20-s duration groups (G600 to G20). The subjective analysis was performed using 5-point Likert scales. Objective quantitative metrics included the maximum standard uptake value (SUV max ), SUV mean , standard deviation (SD), signal-to-noise ratio (SNR), and SNR norm of the background. The variabilities in lesion SUV mean , SUV max , and tumor-to-background ratio (TBR) were also calculated. Results The overall image quality scores in the G600, G300, G180, and G60 groups were 4.9 ± 0.2, 4.9 ± 0.3, 4.4 ± 0.5, and 3.5 ± 0.5 points, respectively. All the lesions identified in the half-dose images were localized in the G60 images, while 56% of the lesions could be clearly identified in the G20 images. With reduced acquisition time, the SUV max and SD of the backgrounds were gradually increased, while the TBR values showed no statistically significant differences among the groups (all p > 0.1). Using the half-dose images as a reference, the variability in the lesion SUV max gradually increased from the G180 to G20 images, while the lesion SUV mean remained stable across all age groups. SNR norm was highly negatively correlated with age. Conclusion Total-body PET/CT with a half dose of [ 18 F]-FDG (1.85 MBq/kg, estimated whole-body effective dose: 1.76–2.57 mSv) achieved good performance in pediatric patients, with sufficient image quality and good lesion conspicuity. Sufficient image quality and lesion conspicuity could be maintained at a fast scanning time of 60 s with half-dose activity.