Does dual-time-point 18 F-FDG PET/CT scan add in the diagnosis of hepatocellular carcinoma?

Objective: The aim of this study was to evaluate the usefulness of dual-time-point F-18-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) with semiquantitative analyses for patients with hepatocellular carcinoma (HCC). Subjects and Methods: The 150 patients with clinically suspected liver malignancies underwent dual-time-point F-18-FDG PET/CT imaging. The maximum standardized uptake value (SUVmax) was calculated at both time points of PET imaging. The change in SUV max (retention index, RI) was defined as the ratio of increase in SUVmax between the early and delayed scans to the SUVmax in the early scan. The tumor-to-normal liver tissue (T/N) ratio of the early and delayed scan was also calculated. The final diagnoses were confirmed by histopathology. A hundred and twenty four patients had HCC, 4 with grade I, 64 with grade II, 55 with grade III and 1 with grade IV. Twenty six patients had benign liver diseases. Results: There were significant differences in the SUVmax and T/N between the early scan and the delayed scan in the HCC Group (t=4.23, P<0.01; t=6.02, P<0.01). There were no significant differences in the SUVmax or T/N of the early and delayed scans in the benign Group (t=1.20, P=0.24; t=1.63, P=0.12). There was no significant difference in the RI of the HCC Group and that of the benign Group (t=0.52, P=0.60). The SUVmax of the delayed scan was significantly higher than that of the early scan for both Groups (t=3.01, P<0.01 for grade III Group; t=2.93, P<0.01 for grade II Group). Significant differences were detected between the grade III Group and the grade II Group for the SUVmax on the early scan and the delayed scan (t=2.15, P<0.01 for early scan; t=2.11, P<0.01 for the delayed scan). There were no significant differences between the grade III and grade II Groups for the retention index of SUVmax (RI-SUVmax) (t=0.06, P=0.95). The T/N ratio on the delayed scan was significantly higher than that on the early scan for both Groups (t=4.21, P<0.01 for grade III Group; t=4.44, P<0.01 for grade II Group). Significant differences were also detected between the grade III and grade II Groups for the T/N ratio on the early and delayed scans (t=2.69, P<0.01 for the early scan; t=2.06, P<0.01 for the delayed scan). Conclusion: Dual time-point F-18-FDG PET/CT scan with semiquantitative analysis of SUVmax and T/N ratio may support the diagnosis of non-invasive HCC indicating its grade of malignancy.