Correlation of dual-tracer PET/CT-based metabolic phenotype and the signal intensity at each MRI phase in hepatocellular carcinoma

Introduction: Metabolic phenotypes of ¹¹C-acetate and ¹⁸F-FDG PET/CT differ according to the degree of tumor cellular differentiation in patients with hepatocellular carcinoma (HCC). We investigated whether imaging patterns in MRI could be related to the tumor differentiation evaluated with dual-tracer PET/CT.

Methods: A total of 35 HCC lesions were retrospectively analyzed from 28 patients who underwent both dual-tracer PET/CT and gadoxetate-enhanced MRI. The HCC lesions were classified into two groups according to the degree of tracer avidity: acetate-dominant or FDG-dominant groups. The signal intensity in HCC lesions was measured with the percentage signal ratio (PSR) at each MRI phase. PSR was defined as the ratio of signal intensity of adjacent normal liver parenchyma to that of the lesion. We compared the difference in signal intensity at each MRI phase between the two groups.

Results: A total of 20 acetate-dominant lesions and 15 FDG-dominant lesions were identified on dual-tracer PET/CT. The median PSR at each MRI phase was significantly different between the two groups: arterial (59.7 vs. 104.9, P < 0.001), portal (103.8 vs. 133.8, P < 0.001), and delayed (114.6 vs. 139.3, P = 0.016) phases, respectively. However, there was no significant difference in the hepatobiliary phase (159.4 vs. 153.5, P = 0.504).

Conclusions: Except for the hepatobiliary phase, MRI-based signal intensity was related to metabolic phenotype on dual-tracer PET/CT. Especially, the arterial phase on MRI could best differentiate the metabolic predominance of HCC.