PurposeTo explore the effect of half 18 F-FDG dose on image quality of pediatric oncological patients using totalbody PET/CT. and investigate the ultra-low dose of administered tracer activity. Methods 100 pediatric oncological patients who underwent total-body PET/CT using the uEXPLORER scanner with half 18 F-FDG dose (1.85 MBq/kg) were retrospectively enrolled. The PET images were rstly reconstructed using all the 600s data, and then split into 300s, 180s, 60s, 40s and 20s duration groups. The subjective analysis method was assessed using a 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 backgrounds. The variability in lesion SUV mean , SUV max , and tumor-to-background ratio (TBR) were also calculated.
ResultsThe overall image quality scores in Group 600s, 300s, 180s and 60s were 4.9 ± 0.2, 4.9 ± 0.3, 4.4±0.5 and 3.5±0.5 respectively. All the lesions identi ed in half-dose images were localised down to G60s (1/20-dose) images; while 56% of the lesion could be clearly identi ed in G20s (1/60-dose) images. With stimulated reduced doses, SUV max and SD of backgrounds were gradually increased, while TBR values showed no statistically signi cant deviation among all the groups (all p > 0.1). Using the half-dose images as reference, the variability of lesion SUV max gradually increased from G180s to G20s, while lesion SUVmean remained stable for all the age groups. SNR norm was highly correlated with the age in a negative direction.
ConclusionsThe total-body PET/CT with half 18 F-FDG dose achieved good performance in pediatric patients considering the su cient image quality and lesion conspicuity. Su cient image quality and lesion conspicuity could be maintained with an administered dose reduced down to 1/20-dose (0.185 MBq/kg, , estimated effective dose: 0.18-0.26 mSv).