Variability and reproducibility of hepatic FDG uptake measured as SUV as well as tissue‐to‐blood background ratio using positron emission tomography in healthy humans

Introduction: To investigate variability and reproducibility of hepatic [¹⁸F]‐2‐fluoro‐2‐deoxy‐d ‐glucose (FDG) uptake in healthy individuals. Methods:  Static images were obtained 70 min after the injection of 160 MBq FDG in six healthy subjects at two occasions with 13 days’ interval. FDG uptake was adjusted for tissue‐to‐blood background ratio (T/B), or measured as standardized uptake value (SUV). Small regions of interest (ROIs) of 10 cm³ in two different hepatic regions were analysed as well as the total liver. Results: Mean SUV was 1·16 ± 0·15 and mean T/B corrected values was 1·87 ± 0·17. The maximal values were 2·70 (SUV) and 4·67 (T/B). Reproducibility was 6·7% for the mean SUV and 0·2% for the max SUV values. The corresponding figures for the T/B corrected mean values were 6·4% and for the max T/B values 13·0%. In general, the small ROIs had a comparable or even lower CV% for SUV values, but a higher CV% for T/B corrected values. Conclusions: In normal subjects hepatic FDG‐uptake is high and homogeneous with a low CV% between days. T/B corrected values are largely comparable to SUV values but not superior, probably due to the standardization of procedures and homogeneity of the subjects. The T/B corrected method is theoretically superior in a more inhomogeneous population or when using different scanners and is shown here to be easy to apply. Small ROIs of 10 cm³ are representative with respect to mean FDG uptake in the total liver and reproducibility, but do not identify the max FDG uptake.