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

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.

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).

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.