Metabolic liver function in humans measured by 2-18F-fluoro-2-deoxy-D-galactose PET/CT–reproducibility and clinical potential

BACKGROUND PET/CT with the radioactively labelled galactose analogue 2-18F-fluoro-2-deoxy-D-galactose (18F-FDGal) can be used to quantify the hepatic metabolic function and visualise regional metabolic heterogeneity. We determined the day-to-day variation in humans with and without liver disease. Furthermore, we examined whether the standardised uptake value (SUV) of 18F-FDGal from static scans can substitute the hepatic systemic clearance of 18F-FDGal (K met, mL blood/min/mL liver tissue/) quantified from dynamic scans as measure of metabolic function. Four patients with cirrhosis and six healthy subjects underwent two 18F-FDGal PET/CT scans within a median interval of 15 days for determination of day-to-day variation. The correlation between K met and SUV was examined using scan data and measured arterial blood concentrations of 18F-FDGal (blood samples) from 14 subjects from previous studies. Regional and whole-liver values of K met and SUV along with total metabolic liver volume and total metabolic liver function (total SUV, average SUV multiplied by total metabolic liver volume) were calculated. RESULTS No significant day-to-day differences were found for K met or SUV. SUV had higher intraclass correlation coefficients than K met (0.92-0.97 vs. 0.49-0.78). The relationship between K met and SUV was linear. Total metabolic liver volume had non-significant day-to-day variation (median difference 50 mL liver tissue; P = 0.6). Mean total SUV in healthy subjects was 23,840 (95% CI, 21,609; 26,070), significantly higher than in the patients (P < 0.001). CONCLUSIONS The reproducibility of 18F-FDGal PET/CT was good and SUV can substitute K met for quantification of hepatic metabolic function. Total SUV of 18F-FDGal is a promising tool for quantification of metabolic liver function in pre-treatment evaluation of individual patients.