The evaluation on the image quality of a total-body PET/CT imaging with an ultra-low injected dose

Purpose: The purpose of this study was to evaluate the image quality of ultra-low injected dose in total-body PET/CT oncological studies.

Methods: Sixteen oncological patients were prospectively enrolled in the ultra-low dose PET imaging study. All patients were instructed to fast 6h prior to the scan with a fast glucose level less than 7.0mmol/L, and then administrated with an ultra-low dose of ¹⁸F-FDG (0.37MBq/kg).[1] The images were acquired with a 15min acquisition duration on a total-body PET-CT scanner (uEXPLORER, United Imaging Healthcare). The PET images were first reconstructed using all 15min data and further segmented into 1min, 2min, 4min, 8min and 10min durations, referred as G1, G2, G4, G8, G10, and G15. Image quality was assessed by two experienced nuclear physicians with over 5 years of interpreting PET/CT images using a 5-point Likert scale. (1, unacceptable image quality; 2, poor image quality; 3, acceptable image quality; 4, good image quality; 5, excellent image quality). The lesion SUVmax, liver SUVmax, SUVmean and SD were measured, and tumor-to-background ratio (TBR) and liver signal-to-noise ratio (SNR) were obtained. Statistical analysis were performed between the different groups.

Results: Qualitative and quantitative analysis of image quality had a substantial or perfect agreement (all kappa>0.7). The image quality scores between groups were significantly different (P<0.001). The image quality of G8, G10 and G15 was superior to that of G1, G2, and G4 in the qualitative analysis. And the image quality was clinically acceptable with the acquisition time of 8 minutes and above. The liver SUVmean showed no significant differences among all the groups (P>0.05). However, liver SNR increased with the acquisition duration, and no significant differences of both were found between G8, G10 and G15 groups. Lesion SUVmax and TBR increased slightly with the acquisition duration without significant differences (all P>0.05).

Conclusions: Ultra-low dose with 8-min acquisition is feasible for total-body PET/CT study from the qualitative and quantitative aspects and successfully meet the clinical diagnostic requirements.