PET/CT in patients with liver lesions of different nature

Abstract

Although FDG PET/CT evaluation of liver nodules still has limited application in routine clinical practice compared with the conventional imaging modalities (US, CT and MRI), it nevertheless seems to have certain potentially useful roles in this setting. Two major determinants of the diagnostic sensitivity of PET/CT in hepatocellular carcinoma (HCC) are (1) the degree of differentiation (related to varying levels of glucose transporters and glucose-6-phosphatase activity, with well-differentiated tumors being suggested to show low expression of GLUT and high dephosphorylating enzyme activity and undifferentiated tumors to show high expression of glucose transporters and low dephosphorylating enzyme activity), and (2) the size of the lesion. The diagnostic efficacy of FDG PET/CT could be enhanced on delayed imaging. An inverse correlation has been described between FDG PET/CT and choline/acetate PET. The literature underlines the role of choline and acetate in detecting and staging well- or moderately differentiated HCC, in which these PET tracers demonstrate better efficacy compared with FDG. The dual-tracer approach using tracers like FDG and acetate is suggested to provide the best diagnostic accuracy. Disease prognostication and staging of extrahepatic metastasis both benefit from whole-body staging with FDG PET/CT. In cholangiocarcinoma, the major factors determining the sensitivity of FDG PET/CT are (1) hilar versus peripheral subtype and (2) nodular versus infiltrating morphology. FDG PET/CT can serve an adjunct to conventional imaging in differentiating benign from malignant lesions, with hemangioma, FNH, and hepatic adenoma usually showing tracer accumulation similar to, or lower than, the background physiological liver activity although a small number of false positives are observed. The non-FDG tracers have been investigated in this setting in a limited number of patients and have been found not to be of incremental value. © 2014 Italian Association of Nuclear Medicine and Molecular Imaging.