Variability and Reliability of Normal Liver 18F-FDG Standardized Uptake Value in Relation to Placement of Volume of Interest

Background: The impact of volume-of-interest (VOI) placement on liver standardized-uptake-value (SUV) measurement remains unclear. Objectives: To investigate variability and reliability of liver SUV in relation to placement of VOI within the right lobe of the liver. Patients and Methods: Positron emission tomography-computed tomography (PET/CT) of 343 patients with normal liver were retrieved. Liver mean SUV (SUVmean) were measured by placing spherical VOIs at upper, portal vein and lower level of the right-lobe liver. The general linear model, Bland-Altman analysis, one-way ANOVA were performed and the intraclass correlation coefficients (ICC) were calculated to identify impacts of reader and VOI position on variations of liver SUVmean. Results: The liver SUVmean at the upper, lower and portal vein level were 1.85 +/- 0.435,1.88 +/- 0.409, and 1.89 +/- 0.414, respectively, with no significant inter-location difference (P = 0.449). The coefficients of variation were close among locations (21.9% - 23.5%). The inter-location ICCs controlling for reader were 0.955 for reader 1 and 0.980 for reader 2, while the inter-reader ICCs controlling for location were between 0.930 and 0.937, indicating great reliability and reproducibility. However, inter-reader bias of SUVmean were significantly different among locations (P < 0.001). Bias at portal vein level (0.069 +/- 0.112) was significantly larger than those at the upper level (0.004 +/- 0.144, P < 0.001) and lower level (0.002 +/- 0.136, P < 0.001). Conclusion: Liver SUVmean measured by placing VOI at the portal vein level exhibited a relatively larger variation and less precision between readers, which was not recommended.