Optimal 2-[(18)F]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-[(18)F]fluoro-2-deoxy-d-galactose ((18)F-FDGal) may improve diagnosis of hepatocellular carcinoma (HCC). The aim of this study was to test which of three different (18)F-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 (VOIs) encircling HCC tumours on contrast-enhanced CT (ce-CT) images. Three PET/CT protocols were conducted following an intravenous (18)F-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 T(peak)/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 (18)F-FDGal injection offered an advantage to traditional whole-body PET/CT images acquired after 1 h for detection of HCC.