Optimal 2-[18F]fluoro-2-deoxy-D-galactose PET/CT protocol for detection of hepatocellular carcinoma

Background: Positron emission tomography (PET) with the liver-specific galactose tracer 2-[F-18] fluoro-2-deoxy-D-galactose (F-18-FDGal) may improve diagnosis of hepatocellular carcinoma (HCC). The aim of this study was to test which of three different F-18-FDGal PET protocols gives the highest tumour-to-background (T/B) ratio on PET images and thus better detection of HCC tumours. Methods: Ten patients with a total of 15 hepatic HCC tumours were enrolled prior to treatment. An experienced radiologist defined volumes of interest (VOls) encircling HCC tumours on contrast-enhanced CT (ce-CT) images. Three PET/CT protocols were conducted following an intravenous F-18-FDGal injection: (i) a 20-min dynamic PET/CT of the liver (to generate a 3D metabolic image), (ii) a traditional static whole-body PET/CT after 1 h, and (iii) a late static whole-body PET/CT after 2 or 3 h. PET images from each PET/CT protocol were fused with ce-CT images, and the average standardized uptake values (SUV) in tumour and background liver tissue were used to calculate (T/B) ratios. Furthermore, T-peak/B ratios were calculated using the five hottest voxels in all hot tumours. The ratios for the three different PET protocols were compared. Results: For the individual tumours, there was no significant difference in the T/B ratio between the three PET protocols. The metabolic image yielded higher Tpeak/B ratios than the two static images, but it was easier to identify tumours on the static images. One extrahepatic metastasis was detected. Conclusions: Neither metabolic images nor static whole-body images acquired 2 or 3 h after F-18-FDGal injection offered an advantage to traditional whole-body PET/CT images acquired after 1 h for detection of HCC.