Two-time-point FDG PET/CT: Liver SUL_meanrepeatability

Objective. The purpose of this study was to evaluate the repeatability of liver mean standardized uptake value normalized to lean body mass (SUL_mean) in the same patients at different time points within the right lobe of the liver at ₁₈F-FDG PET/CT, in a clinical setting, Materials and methods. Two PET/CT studies performed on two different dates from each of 130 patients who had normal livers according to structural imaging were included in this reader study. The mean (± SD) length of time between the studies was 235 ± 192 days. SUL_mean was measured with a 30-mm diameter spherical volume of interest (VOI) placed within the right lobe of the liver (above, betow, and at the levet of the main portal vein) by two expert readers. ANOVA, intraclass corretation coeflicient (ICC), and Bland-Altman analysis were performed. Results. The ICC for the first and second set of studies varied between 0.487 and 0.535 for reader 1 and between 0.472 and 0.545 for reader 2. The mean percentage variation for SUL_meanbetween the two time scans for the VOls placed above, betow, and at the levet of the main portal vein were 3.55% ± 23.19%, 4.65% ± 23.87%, and 4.30% ± 23.03%, respectivety, for reader 1 and 4.49% ± 23.23%, 4.33%. ± 23.74%, and 4.48% ± 23.01%., respectivety, for reader 2. Using 95% CI, the reference range for intrapatient variations between the studies in liver SUL_mean was-0.5 to 0.60. Conclusion. There is only fair repeatability of liver SUL_mean measured between two time points in the same patient in a clinical setting. Scan-to-scan intrapatient variation in absolute liver SUL_mean was -0.5 to 0.60.